Aura Open Source Developer

Guide

Last updated: November 1, 2017

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CONTENTS

Chapter 1: What is Aura? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Why Use Aura? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Aura Version Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Chapter 2: Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Create an Aura App from the Command Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Import an Aura App into Eclipse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Add a Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Build Aura from Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Chapter 3: Creating Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Component Markup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Component Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Viewing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Component Bundles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Component IDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
HTML in Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
CSS in Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Component Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Component Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Component Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Component Facets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Best Practices for Conditional Markup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Component Versioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Using Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Dynamic Output in Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Conditional Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Data Binding Between Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Value Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Expression Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Expression Operators Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Expression Functions Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Using Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
$Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Input Component Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Dynamically Populating Label Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Contents

Getting Labels in JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Setting Label Values via a Parent Attribute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Customizing your Label Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Providing Component Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Working with UI Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Event Handling in UI Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Using the UI Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Working with the Flow Lightning Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Set Flow Variable Values from a Lightning Component . . . . . . . . . . . . . . . . . . . . . . . . 79
Get Flow Variable Values to a Lightning Component . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Control a Flow’s Finish Behavior in a Lightning Component . . . . . . . . . . . . . . . . . . . . . 83
Resume a Flow Interview from a Lightning Component . . . . . . . . . . . . . . . . . . . . . . . . 84
Supporting Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Button Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Carousels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Help and Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Audio Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Forms, Fields, and Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Dialog Overlays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Menus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Resolving Accessibility Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Add Components to Apps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Chapter 4: Communicating with Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Actions and Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Handling Events with Client-Side Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Component Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Component Event Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Create Custom Component Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Fire Component Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Handling Component Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Component Event Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Application Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Application Event Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Create Custom Application Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Fire Application Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Handling Application Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Application Event Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Event Handling Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Advanced Events Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Firing Aura Events from Non-Aura Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Contents

Events Best Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Events Anti-Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Events Fired During the Rendering Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
System Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Chapter 5: Creating Apps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

App Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Designing App UI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Creating App Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Developing Secure Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
What is LockerService? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Styling Apps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Using External CSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
More Readable Styling Markup with the join Expression . . . . . . . . . . . . . . . . . . . . . . . 141
Vendor Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Styling with Flavors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Styling with Tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Using JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Invoking Actions on Component Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Sharing JavaScript Code in a Component Bundle . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Using External JavaScript Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Creating Reusable JavaScript Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Working with Attribute Values in JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Working with a Component Body in JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Working with Events in JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Modifying the DOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Client-Side Runtime Binding of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
Checking Component Validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Modifying Components Outside the Framework Lifecycle . . . . . . . . . . . . . . . . . . . . . . 169
Validating Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
Throwing and Handling Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
Calling Component Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Using JavaScript Promises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Making API Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
JavaScript Cookbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Dynamically Creating Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Detecting Data Changes with Change Handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Finding Components by ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
Dynamically Adding Event Handlers To a Component . . . . . . . . . . . . . . . . . . . . . . . . 187
Creating a Document-Level Event Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Dynamically Showing or Hiding Markup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Adding and Removing Styles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
Which Button Was Pressed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Formatting Dates in JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Contents

Using Java . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

Essential Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Reading Initial Component Data with Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Creating Server-Side Logic with Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
Server-Side Rendering to the DOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Server-Side Runtime Binding of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Serializing Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Java Cookbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
Dynamically Creating Components in Java . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
Setting a Component ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Getting a Java Reference to a Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Lightning Container . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Using a Third-Party Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
Lightning Container Component Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
The Lightning Realty App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
lightning-container NPM Module Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Controlling Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
Application Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
Interface Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
Component Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
Attribute Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
Event Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
URL-Centric Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Using Custom Events in URL-Centric Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Accessing Tokenized Event Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Using Object-Oriented Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
What is Inherited? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Inherited Component Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Abstract Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
Inheritance Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
Caching with Storage Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
Storage Service Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Initializing Storage Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Using Storage Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Using the AppCache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

TESTING AND DEBUGGING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

Chapter 6: Testing and Debugging Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
JavaScript Test Suite Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
Pass a Controller Action in Component Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
Fail a Test Only When Expected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Contents

Debugging Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

Utility Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
Sample Test Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Mocking Java Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Mocking Java Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
Mocking Java Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
Mocking Java Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

Chapter 7: Customizing Behavior with Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

Modes Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
Controlling Available Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Setting the Default Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Setting the Mode for a Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

Chapter 8: Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

Log Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
Warning Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

Chapter 9: Fixing Performance Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

<aura:if>—Clean Unrendered Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
<aura:iteration>—Multiple Items Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

Chapter 10: Measuring Performance with MetricsService . . . . . . . . . . . . . . . . . . . . . 303

Adding Performance Transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
Adding Performance Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Logging Data with Beacons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Abstracting Measurement with Plugins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
End-to-End MetricsService Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Step 1: Create a Beacon Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Step 2: Add a Transaction and Mark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

CUSTOMIZING AURA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

Chapter 11: Plugging in Custom Code with Adapters . . . . . . . . . . . . . . . . . . . . . . . . . 311
Default Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
Overriding Default Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

Chapter 12: Accessing Components from Non-Aura Containers . . . . . . . . . . . . . . . . 314

Add an Aura button inside an HTML div container . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

Chapter 13: Customizing Data Type Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . 316

Registering Custom Converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Custom Converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318

Chapter 14: Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

Reference Doc App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Contents

Supported aura:attribute Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

Basic Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
Function Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Object Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Collection Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Custom Java Class Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
Framework-Specific Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
aura:application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
aura:component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
aura:clientLibrary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
aura:dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
aura:event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
aura:if . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
aura:interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
aura:iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
aura:method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
aura:renderIf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
aura:set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Setting Attributes Inherited from a Super Component . . . . . . . . . . . . . . . . . . . . . . . . . 341
Setting Attributes on a Component Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
Setting Attributes Inherited from an Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Messaging Component Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
lightning:notificationsLibrary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
lightning:overlayLibrary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
System Event Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
aura:doneRendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
aura:doneWaiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
aura:locationChange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
aura:systemError . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
aura:valueChange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
aura:valueDestroy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
aura:valueInit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
aura:valueRender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
aura:waiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
Supported HTML Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
Anchor Tag: <a> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Chapter 15: Aura Request Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Initial Application Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
Component Request Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Component Request Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Server-Side Processing for Component Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Contents

Client-Side Processing for Component Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

Component Request Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
CHAPTER 1 What is Aura?
In this chapter ... Aura is a UI framework for developing dynamic web apps for mobile and desktop devices. It’s a modern
framework for building single-page applications engineered for growth.
• Why Use Aura?
The framework supports partitioned multi-tier component development that bridges the client and
• Components
server. It uses JavaScript on the client side and Java on the server side.
• Events
• Aura Version
Numbers

1
What is Aura? Why Use Aura?

Why Use Aura?

The benefits include an out-of-the-box set of components, event-driven architecture, and a framework optimized for performance.
Out-of-the-Box Component Set
Comes with an out-of-the-box set of components to kick start building apps. You don't have to spend your time optimizing your
apps for different devices as the components take care of that for you.
Performance
Uses a stateful client and stateless server architecture that relies on JavaScript on the client side to manage UI component metadata
and application data. The client calls the server only when absolutely necessary; for example to get more metadata or data. The
server only sends data that is needed by the user to maximize efficiency. The framework uses JSON to exchange data between the
server and the client. It intelligently utilizes your server, browser, devices, and network so you can focus on the logic and interactions
of your apps.
Event-driven architecture
Uses an event-driven architecture for better decoupling between components. Any component can subscribe to an application
event, or to a component event they can see.
Faster development
Empowers teams to work faster with out-of-the-box components that function seamlessly with desktop and mobile devices. Building
an app with components facilitates parallel design, improving overall development efficiency. Aura provides the basic constructs of
inheritance, polymorphism, and encapsulation from object-oriented programming and applies them to presentation layer development.
The framework enables you to extend a component or implement a component interface.
Components are encapsulated and their internals stay private, while their public shape is visible to consumers of the component.
This strong separation gives component authors freedom to change the internal implementation details and insulates component
consumers from those changes.
Device-aware and cross browser compatibility
Apps use responsive design and provide an enjoyable user experience. Aura supports the latest in browser technology such as
HTML5, CSS3, and touch events.

Components
Components are the self-contained and reusable units of an app. They represent a reusable section of the UI, and can range in granularity
from a single line of text to an entire app.
The framework includes a set of prebuilt components. You can assemble and configure components to form new components in an
app. Components are rendered to produce HTML DOM elements within the browser.
A component can contain other components, as well as HTML, CSS, JavaScript, or any other Web-enabled code. This enables you to
build apps with sophisticated UIs.
The details of a component's implementation are encapsulated. This allows the consumer of a component to focus on building their
app, while the component author can innovate and make changes without breaking consumers. You configure components by setting
the named attributes that they expose in their definition. Components interact with their environment by listening to or publishing
events.

SEE ALSO:
Creating Components

2
What is Aura? Events

Events
Event-driven programming is used in many languages and frameworks, such as JavaScript and Java Swing. The idea is that you write
handlers that respond to interface events as they occur.
A component registers that it may fire an event in its markup. Events are fired from JavaScript controller actions that are typically triggered
by a user interacting with the user interface.
There are two types of events in the framework:
• Component events are handled by the component itself or a component that instantiates or contains the component.
• Application events are handled by all components that are listening to the event. These events are essentially a traditional
publish-subscribe model.
You write the handlers in JavaScript controller actions.

SEE ALSO:
Communicating with Events
Handling Events with Client-Side Controllers

Aura Version Numbers

Aura uses version numbers that are consistent with other Maven projects. This makes it easy for projects built with Maven to express
their dependency on Aura.
The version number scheme is:
major.minor[.incremental][-qualifier]
The major, minor, and optional incremental parts are all numeric. The qualifier string is optional. For example, 1.2.0,
2.4, or 2.5.0-SNAPSHOT are all valid.
The major number advances and the minor and incremental counters reset to zero for releases with large functional changes.
Within a major release, the minor number advances for small updates with enhancements and bug fixes. The incremental
counter is only used for targeted fixes, usually for critical bugs.
The qualifier string is largely arbitrary. A version number that includes a qualifier is a non-release build. The compatibility
guarantee is weaker, because the build is stabilizing towards a release. In order of increasing stability, the qualifier may be:
SNAPSHOT
An arbitrary development build. There are no assurances for such a build, as its under active development.
msN
A milestone build. Some features can at least be demonstrated, but the build isn't ready for a full release. Feature behavior may
change as the milestone progresses towards a release.
rcN
A release candidate, which is a build we think is close to a final release. However, it's still undergoing final checking and may change
before an unqualified release.
A release build has a fixed major, minor, and incremental version. It's newer and preferable to any unqualified version with
the same version number. For example, x.y.z is newer than x.y.z-SNAPSHOT.
Release candidates are always newer than any milestone, and a release candidate or milestone with a higher number is newer than
others with lower numbers.

3
What is Aura? Aura Version Numbers

If you have the source code for the Aura framework, you can find the version number in the root folder's pom.xml file. For example:
<project ... >
<name>Aura Framework</name>
<version>0.273</version>
</project>

Although it will rarely be important, you can use the Java ConfigAdapter.getAuraVersion() method to see what version
of Aura is running your code.

4
CHAPTER 2 Quick Start
In this chapter ... The quick start steps you through building and running your first Aura app from the command line, or
in the Eclipse IDE. Choose the method you're most comfortable with and check out the next steps after
• Create an Aura App you build an app.
from the Command
Line
• Import an Aura App
into Eclipse
• Next Steps

5
Quick Start Create an Aura App from the Command Line

Create an Aura App from the Command Line

You can generate a basic Aura app quickly using the command line. For details, see the README.md file in the Aura repo.

SEE ALSO:
Import an Aura App into Eclipse
Next Steps

Import an Aura App into Eclipse

This section shows you how to import the Aura app you created in the command-line quick start into Eclipse.

Note: You must complete the command-line quick start before proceeding.

Before you begin, make sure you have this software installed:
1. JDK 1.8
2. Apache Maven 3
3. Eclipse 3.7 or later and the m2eclipse plugin. Choose the Eclipse distribution for Java EE Developers. This includes JavaScript editing
and other Web UI tools.
Step 1: Import the Command-Line Project into Eclipse
1. Click File > Import... > Maven > Existing Maven Projects.
2. Click Next.
3. In the Root Directory field, browse to the helloWorld folder created in the command-line quick start and click OK.
4. Click Finish.
You should now have a new project called helloWorld in the Package Explorer.
Step 2: Build and Run Your Project
1. Click Run > Debug Configurations....
2. Double click Maven Build.
3. Enter these values:
• Name: HelloWorld Server
• Base directory: ${workspace_loc:/helloWorld} (where helloWorld is the same as your Artifact Id)
• Goals: jetty:run

Note: To use another port, such as port 8080, append -Djetty.port=8080 to jetty:run.

4. Click Debug.
You should see a message in the Eclipse Console window indicating that the Jetty server has started.
Step 3: Test Your App
1. Navigate to http://localhost:8080 to test your app.
You will be redirected to http://localhost:8080/helloWorld/helloWorld.app.

6
Quick Start Add a Component

2. Validate that your app is working by looking for "hello web" in the browser page.

Add a Component
An Aura app is represented by a .app file composed of Aura components and HTML tags.
Components are the building blocks in your app and are grouped in a namespace. In addition to the required top-level
<aura:component> tag in a component or <aura:application> tag in an application, you can insert user interface
components using tags defined in the Aura component library.
In Eclipse, we'll add a component to our simple app. The following diagram shows the folder structure for the project. Under the
components folder, there is a helloWorld folder representing the namespace. Under that folder is a sub-folder, also called
helloWorld, which represents the application, which is a special type of component. This folder can also contain resources, such as
CSS and JavaScript files. We will add a new component to the helloWorld namespace.

Note: Component and app names must be unique in the namespace and they don’t have to match the namespace name.

Step 1: Make a New Component

1. In Eclipse Package Explorer, right-click the helloWorld namespace folder under components and select New > File.
2. Create a new hello component in the namespace by entering these values:
Parent folder: helloWorld/src/main/webapp/WEB-INF/components/helloWorld/hello
File name: hello.cmp

Note: We’re adding the component to a new hello folder under the helloWorld namespace folder.

3. Click Finish.

7
Quick Start Next Steps

4. Open hello.cmp and enter:

<aura:component>
Hello, world!
</aura:component>

5. Save the file.

6. View the component in a browser by navigating to http://localhost:8080/helloWorld/hello.cmp. If the
component is not displayed, make sure that the web server is running.
Step 2: Add the Component to the App
Now, we're going to add our new component to the app. In this case, the component is simple, but the intent is to demonstrate how
you can create a component that is reusable in multiple apps.
1. Open helloWorld.app and replace its contents with:
<aura:application>

<h1>My First Aura App</h1>

<helloWorld:hello />

</aura:application>

2. Save the file.

3. View the app in a browser by navigating to http://localhost:8080/helloWorld/helloWorld.app.
You created an app and added a simple component using Eclipse. Aura enables you to use JavaScript on the client and Java on the
server to create rich applications, as you’ll see in later topics.

SEE ALSO:
aura:application
Component Body

Next Steps
Now that you've created your first app, you might be wondering where do I go from here? There is much more to learn about Aura.
Here are a few ideas for next steps.
• Look at the Aura source code and build it from source in Eclipse
• Browse components that come out-of-the-box with Aura.

Build Aura from Source

You don't have to build Aura from source to use it. However, if you want to customize the source code or submit a pull request with
enhancements to the framework, here's how to do it. Before you begin, make sure you have this software installed:
1. JDK 1.8
2. Apache Maven 3
Step 1: Install git

8
Quick Start Build Aura from Source

The Aura source code is available on GitHub. To download the source code, you need an account on GitHub and the git command-line
tool.
1. Create a GitHub account at https://github.com/signup/free.
2. Follow the instructions at https://help.github.com/articles/set-up-git to install and configure git and ssh keys.
You don't have to create your own repository. You'll be cloning the Aura source next.
Step 2: Get and Build Aura Source
1. On the command line, navigate to the directory where you want to keep the Aura source code.
2. Run the following commands to clone the source with git and build it with Maven:
git clone git@github.com:forcedotcom/aura.git
cd aura
mvn install

You should see a message that the build completed successfully.

Step 3: Import Aura Source into Eclipse
You can use your IDE of choice. These instructions show you how to import the Aura source into Eclipse.
1. Install Eclipse 3.7 or later and the m2eclipse plugin. Choose the Eclipse distribution for Java EE Developers. This includes JavaScript
editing and other Web UI tools..
2. Import the Aura source by clicking File > Import > Maven > Existing Maven Projects.
3. Click Next.
4. In the Root Directory field, browse to the directory that you cloned.
5. Click Next.
6. Click Finish.
You should see the source in the Package Explorer.
Step 4: Run Aura from Eclipse
To run Aura's Jetty server from Eclipse:
1. Click Window > Preferences > Maven > Installations > Add...
2. Navigate to your Maven installation and select it.
3. Click Run > Debug Configurations...
4. Right click Maven Build and select New.
5. Enter Aura Jetty in the Name field.
6. In the Base directory field, click Browse Workspace...
7. Select aura-jetty and click OK.

Note: Running aura-jetty enables you to test the doc app and run tests against it. You can’t build custom apps using
this method.

8. Enter jetty:run in the Goals field.

9. Click Apply.
10. Click Debug.

9
Quick Start Build Aura from Source

In the Console window, you should see a message that the Jetty server started. In a browser, navigate to http://localhost:9090/
to access the server.

SEE ALSO:
Reference Doc App

10
CHAPTER 3 Creating Components
In this chapter ... Components are the functional units of Aura.
A component encapsulates a modular and potentially reusable section of UI, and can range in granularity
• Component Markup
from a single line of text to an entire application.
• Component
Namespace
• Viewing Components
• Component Bundles
• Component IDs
• HTML in Components
• CSS in Components
• Component
Attributes
• Component
Composition
• Component Body
• Component Facets
• Best Practices for
Conditional Markup
• Component
Versioning
• Using Expressions
• Using Labels
• Localization
• Providing
Component
Documentation
• Working with UI
Components
• Working with the
Flow Lightning
Component
• Supporting
Accessibility
• Add Components to
Apps

11
Creating Components Component Markup

Component Markup
Component files contain markup and have a .cmp suffix. The markup can contain text or references to other components, and also
declares metadata about the component.
Let's start with a simple "Hello, world!" example in a helloWorld.cmp component.
<aura:component>
Hello, world!
</aura:component>

This is about as simple as a component can get. The "Hello, world!" text is wrapped in the <aura:component> tags, which appear
at the beginning and end of every component definition.
Components can contain most HTML tags so you can use markup, such as <div> and <span>. HTML5 tags are also supported.
<aura:component>
<div class="container">
<!--Other HTML tags or components here-->
</div>
</aura:component>

Note: Case sensitivity should be respected as your markup interacts with JavaScript, CSS, and Java.

Component Naming Rules

A component name must follow these naming rules:
• Must begin with a letter
• Must contain only alphanumeric or underscore characters
• Must be unique in the namespace
• Can’t include whitespace
• Can’t end with an underscore
• Can’t contain two consecutive underscores

Support Level
Each component has a support level ranging from fully supported (GA) to new and experimental (PROTO). The support level is defined
in the support system attribute in the <aura:component> tag. For more information, see the Reference tab.

SEE ALSO:
aura:component
Component Access Control
Create a Custom Renderer
Dynamically Creating Components

12
Creating Components Component Namespace

Component Namespace
Every component is part of a namespace, which is used to group related components together.
Another component or application can reference a component by adding <myNamespace:myComponent> in its markup. For
example, the helloWorld component is in the docsample namespace. Another component can reference it by adding
<docsample:helloWorld /> in its markup.
Note where this component file is stored in the filesystem:
aura-components/components/docsample/helloWorld/helloWorld.cmp
All core components are in the aura-components/components directory. All folders within that directory map to a namespace.
Each folder within a namespace folder maps to a specific component and contains all the resources necessary for the component. We
refer to this folder as the component's bundle.
In this case, the helloWorld bundle only contains a helloWorld.cmp file, which has the markup for this component. See
Component Bundles for more information on files you can include in the bundle.

Namespaces in Code Samples

The code samples throughout this guide use the c namespace. This namespace has no special significance for open source usage. You
can replace the c namespace with any other namespace that you prefer to use for development.
Salesforce developers build Lightning components that are based on the open source Aura framework. The c namespace is the default
namespace if you haven’t set a namespace prefix for your Salesforce organization. Using the c namespace in our code samples makes
it easier for you to reuse the code in both open source Aura components and Lightning components.

Viewing Components
How do we view a component in a Web browser?
In DEV mode, you can address any component using the URL scheme
http://<myServer>/<namespace>/<component>.cmp
1. Start the Jetty server on port 8080.
mvn jetty:run

To use another port, append -Djetty.port=portNumber. For example:

mvn jetty:run -Djetty.port=9877

2. Create a component in aura-components/components/docsample/helloWorld/helloWorld.cmp. Add this

markup to the component.
<!--docsample:helloWorld-->
<aura:component>
Hello, world!
</aura:component>

3. View your component in a browser by navigating to:

http://localhost:8080/helloWorld/helloWorld.cmp
You should see a simple greeting in your browser.

13
Creating Components Component Bundles

4. To stop the Jetty server and free up the port when you are finished, press CTRL+C on the command line.

Component Bundles
A component bundle contains a component or an app and all its related files.

File File Name Usage See Also

Component or Application sample.cmp or The only required resource in a Creating Components on page
sample.app bundle. Contains markup for the 11
component or app. Each bundle aura:application on page 329
contains only one component
or app resource.

CSS Styles sample.css Contains styles for the CSS in Components on page 16
component.

Controller sampleController.js Contains client-side controller Handling Events with Client-Side

methods to handle events in the Controllers on page 98
component.

Documentation sample.auradoc A description, sample code, and Providing Component

one or multiple references to Documentation on page 51
example components

Model sampleModel.js JSON model to initialize a JSON Models on page 199

component.

Renderer sampleRenderer.js Client-side renderer to override Create a Custom Renderer on

default rendering for a page 163
component.

Helper sampleHelper.js Helper methods that are shared Sharing JavaScript Code in a
by the controller and renderer. Component Bundle on page 152

Provider sampleProvider.js Client-side provider that returns Client-Side Runtime Binding of

the concrete component to use Components on page 166
at runtime.

Test Cases sampleTest.js Contains a test suite to be run in Testing and Debugging
the browser. Components on page 250

All resources in the component bundle follow the naming convention and are auto-wired. For example, a controller
<componentName>Controller.js is auto-wired to its component, which means that you can use the controller within the
scope of that component.

Component IDs
A component has two types of IDs: a local ID and a global ID. You can retrieve a component using its local ID in your JavaScript code. A
global ID can be useful to differentiate between multiple instances of a component or for debugging purposes.

14
Creating Components Component IDs

Local IDs
A local ID is an ID that is only scoped to the component. A local ID is often unique but it’s not required to be unique.
Create a local ID by using the aura:id attribute. For example:
<lightning:button aura:id="button1" label="button1"/>

Note: aura:id doesn't support expressions. You can only assign literal string values to aura:id.

Find the button component by calling cmp.find("button1") in your client-side controller, where cmp is a reference to the
component containing the button.
find() returns different types depending on the result.
• If the local ID is unique, find() returns the component.
• If there are multiple components with the same local ID, find() returns an array of the components.
• If there is no matching local ID, find() returns undefined.
To find the local ID for a component in JavaScript, use cmp.getLocalId().

Global IDs
Every component has a unique globalId, which is the generated runtime-unique ID of the component instance. A global ID (1) is
not guaranteed to be the same beyond the lifetime of a component, so it should never be relied on. A global ID can be useful to
differentiate between multiple instances of a component or for debugging purposes.

To create a unique ID for an HTML element, you can use the globalId as a prefix or suffix for your element. For example:
<div id="{!globalId + '_footer'}"></div>

In your browser’s developer console, retrieve the element using document.getElementById("<globalId>_footer"),

where <globalId> is the generated runtime-unique ID.
To retrieve a component’s global ID in JavaScript, use the getGlobalId() function.
var globalId = cmp.getGlobalId();

SEE ALSO:
Finding Components by ID
Which Button Was Pressed?

15
Creating Components HTML in Components

HTML in Components
An HTML tag is treated as a first-class component by the framework. Each HTML tag is translated into an <aura:html> component,
allowing it to enjoy the same rights and privileges as any other component.
For example, the framework automatically converts a standard HTML <div> tag to this component:
<aura:html tag="div" />

You can add HTML markup in components. Note that you must use strict XHTML. For example, use <br/> instead of <br>. You can
also use HTML attributes and DOM events, such as onclick.

Warning: Some tags, like <applet> and <font>, aren’t supported. For a full list of unsupported tags, see Supported HTML
Tags on page 357.

Unescaping HTML
To output pre-formatted HTML, use aura:unescapedHTML. For example, this is useful if you want to display HTML that is generated
on the server and add it to the DOM. You must escape any HTML if necessary or your app might be exposed to security vulnerabilities.
You can pass in values from an expression, such as in <aura:unescapedHtml value="{!v.note.body}"/>.
{!expression} is the framework's expression syntax. For more information, see Using Expressions on page 25.

SEE ALSO:
Supported HTML Tags
CSS in Components

CSS in Components
Style your components with CSS.
To add CSS to a component, add a new file to the component bundle called <componentName>.css. The framework automatically
picks up this new file and auto-wires it when the component is used in a page.
For external CSS resources, see Styling Apps on page 140.
All top-level elements in a component have a special THIS CSS class added to them. This, effectively, adds namespacing to CSS and
helps prevent one component's CSS from blowing away another component's styling. The framework throws an error if a CSS file doesn't
follow this convention.
Let's look at a sample helloHTML.cmp component. The CSS is in helloHTML.css.
Component source
<aura:component>
<div class="white">
Hello, HTML!
</div>

<h2>Check out the style in this list.</h2>

<ul>
<li class="red">I'm red.</li>

16
Creating Components Component Attributes

<li class="blue">I'm blue.</li>

<li class="green">I'm green.</li>
</ul>
</aura:component>

CSS source
.THIS {
background-color: grey;
}

.THIS.white {
background-color: white;
}

.THIS .red {
background-color: red;
}

.THIS .blue {
background-color: blue;
}

.THIS .green {
background-color: green;
}

Output

The top-level elements, h2 and ul, match the THIS class and render with a grey background. Top-level elements are tags wrapped
by the HTML body tag and not by any other tags. In this example, the li tags are not top-level because they are nested in a ul tag.
The <div class="white"> element matches the .THIS.white selector and renders with a white background. Note that
there is no space in the selector as this rule is for top-level elements.
The <li class="red"> element matches the .THIS .red selector and renders with a red background. Note that this is a
descendant selector and it contains a space as the <li> element is not a top-level element.

SEE ALSO:
Adding and Removing Styles
HTML in Components

Component Attributes
Component attributes are like member variables on a class in Java. They are typed fields that are set on a specific instance of a component,
and can be referenced from within the component's markup using an expression syntax. Attributes enable you to make components
more dynamic.

17
Creating Components Component Attributes

Use the <aura:attribute> tag to add an attribute to the component or app. Let’s look at the following sample,
helloAttributes.app:

<aura:application>
<aura:attribute name="whom" type="String" default="world"/>
Hello {!v.whom}!
</aura:application>

All attributes have a name and a type. Attributes may be marked as required by specifying required="true", and may also specify
a default value.
In this case we've got an attribute named whom of type String. If no value is specified, it defaults to "world".
Though not a strict requirement, <aura:attribute> tags are usually the first things listed in a component’s markup, as it provides
an easy way to read the component's shape at a glance.
Now, append ?whom=you to the URL and reload the page. The value in the query string sets the value of the whom attribute. Supplying
attribute values via the query string when requesting a component is one way to set the attributes on that component.

Warning: This only works for attributes of type String.

Attribute Naming Rules

An attribute name must follow these naming rules:
• Must begin with a letter or an underscore
• Must contain only alphanumeric or underscore characters

Expressions
helloAttributes.app contains an expression, {!v.whom}, which is responsible for the component's dynamic output.
{!expression} is the framework's expression syntax. In this case, the expression we are evaluating is v.whom. The name of the
attribute we defined is whom, while v is the value provider for a component's attribute set, which represents the view.

Note: Expressions are case sensitive. For example, if you have a custom field myNamespace__Amount__c, you must refer
to it as {!v.myObject.myNamespace__Amount__c}.

Attribute Validation
We defined the set of valid attributes in helloAttributes.app, so the framework automatically validates that only valid attributes
are passed to that component.
Try requesting helloAttributes.app with the query string ?fakeAttribute=fakeValue. You should receive an error
that helloAttributes.app doesn’t have a fakeAttribute attribute.

SEE ALSO:
Supported aura:attribute Types
Using Expressions

18
Creating Components Component Composition

Component Composition
Composing fine-grained components in a larger component enables you to build more interesting components and applications.
Let's see how we can fit components together. We will first create a few simple components: c:helloHTML and
c:helloAttributes. Then, we’ll create a wrapper component, c:nestedComponents, that contains the simple components.
Here is the source for helloHTML.cmp.
<!--c:helloHTML-->
<aura:component>
<div class="white">
Hello, HTML!
</div>

<h2>Check out the style in this list.</h2>

<ul>
<li class="red">I'm red.</li>
<li class="blue">I'm blue.</li>
<li class="green">I'm green.</li>
</ul>
</aura:component>

CSS source
.THIS {
background-color: grey;
}

.THIS.white {
background-color: white;
}

.THIS .red {
background-color: red;
}

.THIS .blue {
background-color: blue;
}

.THIS .green {
background-color: green;
}

Output

Here is the source for helloAttributes.cmp.

<!--c:helloAttributes-->
<aura:component>

19
Creating Components Component Composition

<aura:attribute name="whom" type="String" default="world"/>

Hello {!v.whom}!
</aura:component>

nestedComponents.cmp uses composition to include other components in its markup.

<!--c:nestedComponents-->
<aura:component>
Observe! Components within components!

<c:helloHTML/>

<c:helloAttributes whom="component composition"/>

</aura:component>

Output

Including an existing component is similar to including an HTML tag. Reference the component by its "descriptor", which is of the form
namespace:component. nestedComponents.cmp references the helloHTML.cmp component, which lives in the c
namespace. Hence, its descriptor is c:helloHTML.
Note how nestedComponents.cmp also references c:helloAttributes. Just like adding attributes to an HTML tag, you
can set attribute values in a component as part of the component tag. nestedComponents.cmp sets the whom attribute of
helloAttributes.cmp to "component composition".

Attribute Passing
You can also pass attributes to nested components. nestedComponents2.cmp is similar to nestedComponents.cmp,
except that it includes an extra passthrough attribute. This value is passed through as the attribute value for c:helloAttributes.
<!--c:nestedComponents2-->
<aura:component>
<aura:attribute name="passthrough" type="String" default="passed attribute"/>
Observe! Components within components!

<c:helloHTML/>

<c:helloAttributes whom="{#v.passthrough}"/>
</aura:component>

Output

helloAttributes is now using the passed through attribute value.

20
Creating Components Component Body

Note: {#v.passthrough} is an unbound expression. This means that any change to the value of the whom attribute in
c:helloAttributes doesn’t propagate back to affect the value of the passthrough attribute in
c:nestedComponents2. For more information, see Data Binding Between Components on page 27.

Definitions versus Instances

In object-oriented programming, there’s a difference between a class and an instance of that class. Components have a similar concept.
When you create a .cmp file, you are providing the definition (class) of that component. When you put a component tag in a .cmp
file, you are creating a reference to (instance of) that component.
It shouldn't be surprising that we can add multiple instances of the same component with different attributes.
nestedComponents3.cmp adds another instance of c:helloAttributes with a different attribute value. The two instances
of the c:helloAttributes component have different values for their whom attribute .
<!--c:nestedComponents3-->
<aura:component>
<aura:attribute name="passthrough" type="String" default="passed attribute"/>
Observe! Components within components!

<c:helloHTML/>

<c:helloAttributes whom="{#v.passthrough}"/>

<c:helloAttributes whom="separate instance"/>

</aura:component>

Output

Component Body
The root-level tag of every component is <aura:component>. Every component inherits the body attribute from
<aura:component>.
The <aura:component> tag can contain tags, such as <aura:attribute>, <aura:registerEvent>,
<aura:handler>, <aura:set>, and so on. Any free markup that is not enclosed in one of the tags allowed in a component is
assumed to be part of the body and is set in the body attribute.
The body attribute has type Aura.Component[]. It can be an array of one component, or an empty array, but it's always an array.
In a component, use “v” to access the collection of attributes. For example, {!v.body} outputs the body of the component.

Setting the Body Content

To set the body attribute in a component, add free markup within the <aura:component> tag. For example:
<aura:component>
<!--START BODY-->

21
Creating Components Component Facets

<div>Body part</div>
<lightning:button label="Push Me" onclick="{!c.doSomething}"/>
<!--END BODY-->
</aura:component>

To set the value of an inherited attribute, use the <aura:set> tag. Setting the body content is equivalent to wrapping that free
markup inside <aura:set attribute="body">. Since the body attribute has this special behavior, you can omit <aura:set
attribute="body">.
The previous sample is a shortcut for this markup. We recommend the less verbose syntax in the previous sample.
<aura:component>
<aura:set attribute="body">
<!--START BODY-->
<div>Body part</div>
<lightning:button label="Push Me" onclick="{!c.doSomething}"/>
<!--END BODY-->
</aura:set>
</aura:component>

The same logic applies when you use any component that has a body attribute, not just <aura:component>. For example:
<lightning:tabset>
<lightning:tab label="Tab 1">
Hello world!
</lightning:tab>
</lightning:tabset>

This is a shortcut for:

<lightning:tabset>
<lightning:tab label="Tab 1">
<aura:set attribute="body">
Hello World!
</aura:set>
</lightning:tab>
</lightning:tabset>

Accessing the Component Body

To access a component body in JavaScript, use component.get("v.body").

SEE ALSO:
aura:set
Working with a Component Body in JavaScript

Component Facets
A facet is any attribute of type Aura.Component[]. The body attribute is an example of a facet.

22
Creating Components Best Practices for Conditional Markup

To define your own facet, add an aura:attribute tag of type Aura.Component[] to your component. For example, let's
create a new component called facetHeader.cmp.
<!--c:facetHeader-->
<aura:component>
<aura:attribute name="header" type="Aura.Component[]"/>

<div>
<span class="header">{!v.header}</span><br/>
<span class="body">{!v.body}</span>
</div>
</aura:component>

This component has a header facet. Note how we position the output of the header using the v.header expression.
The component doesn't have any output when you access it directly as the header and body attributes aren't set. Let’s create another
component, helloFacets.cmp, that sets these attributes.
<!--c:helloFacets-->
<aura:component>
See how we set the header facet.<br/>

<c:facetHeader>

Nice body!

<aura:set attribute="header">
Hello Header!
</aura:set>
</c:facetHeader>

</aura:component>

Note that aura:set sets the value of the header attribute of facetHeader.cmp, but you don’t need to use aura:set if
you’re setting the body attribute.

SEE ALSO:
Component Body

Best Practices for Conditional Markup

Using the <aura:if> tag is the preferred approach to conditionally display markup but there are alternatives. Consider the performance
cost and code maintainability when you design components. The best design choice depends on your use case.

23
Creating Components Component Versioning

Conditionally Create Elements with <aura:if>

Let’s look at a simple example that shows an error message when an error occurs.
<aura:if isTrue="{!v.isError}">
<div>{!v.errorMessage}</div>
</aura:if>

The <div> component and its contents are only created and rendered if the value of the isTrue expression evaluates to true. If
the value of the isTrue expression changes and evaluates to false, all the components inside the <aura:if> tag are destroyed.
The components are created again if the isTrue expression changes again and evaluates to true.
The general guideline is to use <aura:if> because it helps your components load faster initially by deferring the creation and
rendering of the enclosed element tree until the condition is fulfilled.

Toggle Visibility Using CSS

You can use CSS to toggle visibility of markup by calling $A.util.toggleClass(cmp, 'class') in JavaScript code.
Elements in markup are created and rendered up front, but they’re hidden. For an example, see Dynamically Showing or Hiding Markup.
The conditional markup is created and rendered even if it’s not used, so <aura:if> is preferred.

Dynamically Create Components in JavaScript

You can dynamically create components in JavaScript code. However, writing code is usually harder to maintain and debug than using
markup. Again, using <aura:if> is preferred but the best design choice depends on your use case.

SEE ALSO:
aura:if
Conditional Expressions
Dynamically Creating Components

Component Versioning
Use versioning to change the behavior of a resource, such as a component, while maintaining backwards compatibility for existing users
of the resource. Use versioning in markup in applications, components, interfaces, and events.
You can also use versioning in JavaScript controllers, helpers, and renderers, as well as Java controllers.

Versioning in Component Markup

The {!Version} expression returns the version of the component in its current context. The current context is defined by the
component using the component.
This component uses {!Version} to conditionally change the component behavior depending on its version.
<!--c:versionedComponent-->
<aura:component>
<aura:if isTrue="{!Version > 1.0}">
<c:newVersion />

24
Creating Components Using Expressions

</aura:if>
<c:originalVersion />
</aura:component>

<cOther:consumingComponent> uses the <aura:require> tag to define the version of

<cOther:versionedComponent> that it uses. In this example, it requires version 2.0 of any resource in the c namespace. This
sets the context of <cOther:versionedComponent> to version 2.0.
<!--cOther:consumingComponent-->
<aura:component>
<aura:require namespace="c" version="2.0" />
<c:versionedComponent />
</aura:component>

Note: The {!Version} expression returns a String. Depending on how you define version numbers, you may have to
define your own comparison logic to work with numbers or other version identifiers, such as x.y.z.

Versioning Quick Reference

This table summarizes how to retrieve the current version in different contexts.

Resource Returns Syntax

Markup String {!Version}

JavaScript String cmp.getVersion()

Java String Aura.getContextService().getCurrentContext().getAccessVersion()

Using Expressions
Expressions allow you to make calculations and access property values and other data within component markup. Use expressions for
dynamic output or passing values into components by assigning them to attributes.
An expression is any set of literal values, variables, sub-expressions, or operators that can be resolved to a single value. Method calls are
not allowed in expressions.
The expression syntax is: {!expression}
expression is a placeholder for the expression.
Anything inside the {! } delimiters is evaluated and dynamically replaced when the component is rendered or when the value is
used by the component. Whitespace is ignored.
The resulting value can be a primitive, such as an integer, string, or boolean. It can also be a JavaScript object, a component or collection,
a controller method such as an action method, and other useful results.

Note: If you're familiar with other languages, you may be tempted to read the ! as the "bang" operator, which negates boolean
values in many programming languages. In Aura, {! is simply the delimiter used to begin an expression.
There is a second expression syntax: {#expression}. For more details on the difference between the two forms of expression
syntax, see Data Binding Between Components.

25
Creating Components Dynamic Output in Expressions

Identifiers in an expression, such as attribute names accessed through the view, controller values, or labels, must start with a letter or
underscore. They can also contain numbers or hyphens after the first character. For example, {!v.2count} is not valid, but
{!v.count} is.

Important: Only use the {! } syntax in markup in .app or .cmp files. In JavaScript, use string syntax to evaluate an expression.
For example:
var theLabel = cmp.get("v.label");

If you want to escape {!, use this syntax:

<aura:text value="{!"/>

This renders {! in plain text because the aura:text component never interprets {! as the start of an expression.

IN THIS SECTION:
Dynamic Output in Expressions
The simplest way to use expressions is to output dynamic values.
Conditional Expressions
Here are examples of conditional expressions using the ternary operator and the <aura:if> tag.
Data Binding Between Components
When you add a component in markup, you can use an expression to initialize attribute values in the component based on attribute
values of the container component. There are two forms of expression syntax, which exhibit different behaviors for data binding
between the components.
Value Providers
Value providers are a way to access data. Value providers encapsulate related values together, similar to how an object encapsulates
properties and methods.
Expression Evaluation
Expressions are evaluated much the same way that expressions in JavaScript or other programming languages are evaluated.
Expression Operators Reference
The expression language supports operators to enable you to create more complex expressions.
Expression Functions Reference
The expression language contains math, string, array, comparison, boolean, and conditional functions. All functions are case-sensitive.

Dynamic Output in Expressions

The simplest way to use expressions is to output dynamic values.
Values used in the expression can be from component attributes, literal values, booleans, and so on. For example:
{!v.desc}

In this expression, v represents the view, which is the set of component attributes, and desc is an attribute of the component. The
expression is simply outputting the desc attribute value for the component that contains this markup.
If you're including literal values in expressions, enclose text values within single quotes, such as {!'Some text'}.
Include numbers without quotes, for example, {!123}.

26
Creating Components Conditional Expressions

For booleans, use {!true} for true and {!false} for false.

SEE ALSO:
Component Attributes
Value Providers

Conditional Expressions
Here are examples of conditional expressions using the ternary operator and the <aura:if> tag.

Ternary Operator
This expression uses the ternary operator to conditionally output one of two values dependent on a condition.
<a class="{!v.location == '/active' ? 'selected' : ''}" href="#/active">Active</a>

The {!v.location == '/active' ? 'selected' : ''} expression conditionally sets the class attribute of an HTML
<a> tag, by checking whether the location attribute is set to /active. If true, the expression sets class to selected.

Using <aura:if> for Conditional Markup

This snippet of markup uses the <aura:if> tag to conditionally display an edit button.
<aura:attribute name="edit" type="Boolean" default="true"/>
<aura:if isTrue="{!v.edit}">
<ui:button label="Edit"/>
<aura:set attribute="else">
You can’t edit this.
</aura:set>
</aura:if>

If the edit attribute is set to true, a ui:button displays. Otherwise, the text in the else attribute displays.

SEE ALSO:
Best Practices for Conditional Markup
aura:if

Data Binding Between Components

When you add a component in markup, you can use an expression to initialize attribute values in the component based on attribute
values of the container component. There are two forms of expression syntax, which exhibit different behaviors for data binding between
the components.
This concept is a little tricky, but it will make more sense when we look at an example. Consider a c:parent component that has a
parentAttr attribute. c:parent contains a c:child component with a childAttr attribute that’s initialized to the value
of the parentAttr attribute. We’re passing the parentAttr attribute value from c:parent into the c:child component,
which results in a data binding, also known as a value binding, between the two components.
<!--c:parent-->
<aura:component>

27
Creating Components Data Binding Between Components

<aura:attribute name="parentAttr" type="String" default="parent attribute"/>

<!-- Instantiate the child component -->

<c:child childAttr="{!v.parentAttr}" />
</aura:component>

{!v.parentAttr} is a bound expression. Any change to the value of the childAttr attribute in c:child also affects the
parentAttr attribute in c:parent and vice versa.
Now, let's change the markup from:
<c:child childAttr="{!v.parentAttr}" />

to:
<c:child childAttr="{#v.parentAttr}" />

{#v.parentAttr} is an unbound expression. Any change to the value of the childAttr attribute in c:child doesn’t affect
the parentAttr attribute in c:parent and vice versa.
Here’s a summary of the differences between the forms of expression syntax.
{#expression} (Unbound Expressions)
Data updates behave as you would expect in JavaScript. Primitives, such as String, are passed by value, and data updates for the
expression in the parent and child are decoupled.
Objects, such as Array or Map, are passed by reference, so changes to the data in the child propagate to the parent. However,
change handlers in the parent aren’t notified. The same behavior applies for changes in the parent propagating to the child.
{!expression} (Bound Expressions)
Data updates in either component are reflected through bidirectional data binding in both components. Similarly, change handlers
are triggered in both the parent and child components.

Tip: Bi-directional data binding is expensive for performance and it can create hard-to-debug errors due to the propagation
of data changes through nested components. We recommend using the {#expression} syntax instead when you pass
an expression from a parent component to a child component unless you require bi-directional data binding.

Unbound Expressions
Let’s look at another example of a c:parentExpr component that contains another component, c:childExpr.
Here is the markup for c:childExpr.
<!--c:childExpr-->
<aura:component>
<aura:attribute name="childAttr" type="String" />

<p>childExpr childAttr: {!v.childAttr}</p>

<p><lightning:button label="Update childAttr"
onclick="{!c.updateChildAttr}"/></p>
</aura:component>

Here is the markup for c:parentExpr.

<!--c:parentExpr-->
<aura:component>
<aura:attribute name="parentAttr" type="String" default="parent attribute"/>

28
Creating Components Data Binding Between Components

<!-- Instantiate the child component -->

<c:childExpr childAttr="{#v.parentAttr}" />

<p>parentExpr parentAttr: {!v.parentAttr}</p>

<p><lightning:button label="Update parentAttr"
onclick="{!c.updateParentAttr}"/></p>
</aura:component>

The c:parentExpr component uses an unbound expression to set an attribute in the c:childExpr component.
<c:childExpr childAttr="{#v.parentAttr}" />

When we instantiate childExpr, we set the childAttr attribute to the value of the parentAttr attribute in c:parentExpr.
Since the {#v.parentAttr} syntax is used, the v.parentAttr expression is not bound to the value of the childAttr
attribute.
The c:exprApp application is a wrapper around c:parentExpr.
<!--c:exprApp-->
<aura:application >
<c:parentExpr />
</aura:application>

Navigate to c:exprApp.app in your browser.

Both parentAttr and childAttr are set to “parent attribute”, which is the default value of parentAttr.
Now, let’s create a client-side controller for c:childExpr so that we can dynamically update the component. Here is the source for
childExprController.js.

/* childExprController.js */
({
updateChildAttr: function(cmp) {
cmp.set("v.childAttr", "updated child attribute");
}
})

Navigate to c:exprApp.app in your browser again.

Press the Update childAttr button. This updates childAttr to “updated child attribute”. The value of parentAttr is unchanged
since we used an unbound expression.
<c:childExpr childAttr="{#v.parentAttr}" />

Let’s add a client-side controller for c:parentExpr. Here is the source for parentExprController.js.
/* parentExprController.js */
({
updateParentAttr: function(cmp) {
cmp.set("v.parentAttr", "updated parent attribute");
}
})

Navigate to c:exprApp.app in your browser again.

Press the Update parentAttr button. This time, parentAttr is set to “updated parent attribute” while childAttr is unchanged
due to the unbound expression.

29
Creating Components Data Binding Between Components

Warning: Don’t use a component’s init event and client-side controller to initialize an attribute that is used in an unbound
expression. The attribute will not be initialized. Use a bound expression instead. For more information on a component’s init
event, see Invoking Actions on Component Initialization on page 151.
Alternatively, you can wrap the component in another component. When you instantiate the wrapped component in the wrapper
component, initialize the attribute value instead of initializing the attribute in the wrapped component’s client-side controller.

Bound Expressions
Now, let’s update the code to use a bound expression instead. Change this line in c:parentExpr:
<c:childExpr childAttr="{#v.parentAttr}" />

to:
<c:childExpr childAttr="{!v.parentAttr}" />

Navigate to c:exprApp.app in your browser again.

Press the Update childAttr button. This updates both childAttr and parentAttr to “updated child attribute” even though
we only set v.childAttr in the client-side controller of childExpr. Both attributes were updated since we used a bound
expression to set the childAttr attribute.

Change Handlers and Data Binding

You can configure a component to automatically invoke a change handler, which is a client-side controller action, when a value in one
of the component's attributes changes.
When you use a bound expression, a change in the attribute in the parent or child component triggers the change handler in both
components. When you use an unbound expression, the change is not propagated between components so the change handler is only
triggered in the component that contains the changed attribute.
Let’s add change handlers to our earlier example to see how they are affected by bound versus unbound expressions.
Here is the updated markup for c:childExpr.
<!--c:childExpr-->
<aura:component>
<aura:attribute name="childAttr" type="String" />

<aura:handler name="change" value="{!v.childAttr}" action="{!c.onChildAttrChange}"/>

<p>childExpr childAttr: {!v.childAttr}</p>

<p><lightning:button label="Update childAttr"
onclick="{!c.updateChildAttr}"/></p>
</aura:component>

Notice the <aura:handler> tag with name="change", which signifies a change handler. value="{!v.childAttr}"
tells the change handler to track the childAttr attribute. When childAttr changes, the onChildAttrChange client-side
controller action is invoked.
Here is the client-side controller for c:childExpr.
/* childExprController.js */
({
updateChildAttr: function(cmp) {

30
Creating Components Data Binding Between Components

cmp.set("v.childAttr", "updated child attribute");

},

onChildAttrChange: function(cmp, evt) {

console.log("childAttr has changed");
console.log("old value: " + evt.getParam("oldValue"));
console.log("current value: " + evt.getParam("value"));
}
})

Here is the updated markup for c:parentExpr with a change handler.

<!--c:parentExpr-->
<aura:component>
<aura:attribute name="parentAttr" type="String" default="parent attribute"/>

<aura:handler name="change" value="{!v.parentAttr}" action="{!c.onParentAttrChange}"/>

<!-- Instantiate the child component -->

<c:childExpr childAttr="{!v.parentAttr}" />

<p>parentExpr parentAttr: {!v.parentAttr}</p>

<p><lightning:button label="Update parentAttr"
onclick="{!c.updateParentAttr}"/></p>
</aura:component>

Here is the client-side controller for c:parentExpr.

/* parentExprController.js */
({
updateParentAttr: function(cmp) {
cmp.set("v.parentAttr", "updated parent attribute");
},

onParentAttrChange: function(cmp, evt) {

console.log("parentAttr has changed");
console.log("old value: " + evt.getParam("oldValue"));ui
console.log("current value: " + evt.getParam("value"));
}
})

Navigate to c:exprApp.app in your browser again.

Open your browser’s console (More tools > Developer tools in Chrome).
Press the Update parentAttr button. The change handlers for c:parentExpr and c:childExpr are both triggered as we’re
using a bound expression.
<c:childExpr childAttr="{!v.parentAttr}" />

Change c:parentExpr to use an unbound expression instead.

<c:childExpr childAttr="{#v.parentAttr}" />

Navigate to c:exprApp.app in your browser again.

31
Creating Components Value Providers

Press the Update childAttr button. This time, only the change handler for c:childExpr is triggered as we’re using an unbound
expression.

SEE ALSO:
Detecting Data Changes with Change Handlers
Dynamic Output in Expressions
Component Composition

Value Providers
Value providers are a way to access data. Value providers encapsulate related values together, similar to how an object encapsulates
properties and methods.
The value providers for a component are m (model), v (view), and c (controller).

Value Provider Description See Also

m A component’s model, which enables the component Reading Initial Component Data with Models
to initialize its data from a dynamic source, such as a
database

v A component’s attribute set. This value provider enables Component Attributes

you to access the value of a component’s attribute in the
component’s markup.

c A component’s controller, which enables you to wire up Handling Events with Client-Side Controllers
event handlers and actions for the component

All components have a v value provider, but aren't required to have a controller or model. All three value providers are created
automatically when defined for a component.

Note: Expressions are bound to the specific component that contains them. That component is also known as the attribute value
provider, and is used to resolve any expressions that are passed to attributes of its contained components.

Global Value Providers

Global value providers are global values and methods that a component can use in expressions.

Global Value Description See Also

Provider
globalID The globalId global value provider returns the global Component IDs
ID for a component. Every component has a unique
globalId, which is the generated runtime-unique ID
of the component instance.

$Browser The $Browser global value provider returns $Browser

information about the hardware and operating system
of the browser accessing the application.

32
Creating Components Value Providers

Global Value Description See Also

Provider
$Label The $Label global value provider enables you to access $Label
labels stored outside your code.

$Locale The $Locale global value provider returns information $Locale

about the current user’s preferred locale.

To add your own custom global value providers, see Adding Custom Global Value Providers.

Accessing Fields and Related Objects

Values in a value provider are accessed as named properties. To use a value, separate the value provider and the property name with a
dot (period). For example, v.body. You can access value providers in markup or in JavaScript code.
When an attribute of a component is an object or other structured data (not a primitive value), access the values on that attribute using
the same dot notation.
For example, if a component has an attribute note, access a note value such as title using the v.note.title syntax. This
example shows usage of this nested syntax for a few attributes.
<aura:component>
<aura:attribute name="note" type="java://org.auraframework.demo.notes.Note"/>
<ui:block>
<aura:set attribute="right">
<ui:outputDateTime value="{#v.note.createdOn}" format="h:mm a"/>
</aura:set>
</ui:block>
{!v.note.title}
</aura:component>

Note: {#v.note.createdOn} is an unbound expression. This means that any change to the value attribute in
ui:outputDateTime doesn’t propagate back to affect the value of the note attribute in the parent component. For more
information, see Data Binding Between Components on page 27.
For deeply nested objects and attributes, continue adding dots to traverse the structure and access the nested values.

IN THIS SECTION:
Adding Custom Global Value Providers
Add a custom global value provider by implementing the GlobalValueProviderAdapter interface.

SEE ALSO:
Dynamic Output in Expressions

$Browser
The $Browser global value provider returns information about the hardware and operating system of the browser accessing the
application.

33
Creating Components Value Providers

Attribute Description
formFactor Returns a FormFactor enum value based on the type of hardware the browser is running on.
• DESKTOP for a desktop client
• PHONE for a phone including a mobile phone with a browser and a smartphone
• TABLET for a tablet client (for which isTablet returns true)

isAndroid Indicates whether the browser is running on an Android device (true) or not (false).

isIOS Not available in all implementations. Indicates whether the browser is running on an iOS device (true)
or not (false).

isIPad Not available in all implementations. Indicates whether the browser is running on an iPad (true) or not
(false).

isIPhone Not available in all implementations. Indicates whether the browser is running on an iPhone (true) or
not (false).

isPhone Indicates whether the browser is running on a phone including a mobile phone with a browser and a
smartphone (true), or not (false).

isTablet Indicates whether the browser is running on an iPad or a tablet with Android 2.2 or later (true) or not
(false).

isWindowsPhone Indicates whether the browser is running on a Windows phone (true) or not (false). Note that this
only detects Windows phones and does not detect tablets or other touch-enabled Windows 8 devices.

Example: This example shows usage of the $Browser global value provider.
<aura:component>
{!$Browser.isTablet}
{!$Browser.isPhone}
{!$Browser.isAndroid}
{!$Browser.formFactor}
</aura:component>

Similarly, you can check browser information in a client-side controller using $A.get().
({
checkBrowser: function(component) {
var device = $A.get("$Browser.formFactor");
alert("You are using a " + device);
}
})

$Locale
The $Locale global value provider returns information about the browser's locale.
These attributes are based on Java’s Calendar, Locale and TimeZone classes.

34
Creating Components Value Providers

Attribute Description Sample Value

country The ISO 3166 representation of the country code "US", "DE", "GB"
based on the language locale.

currency The currency symbol. "$"

currencyCode The ISO 4217 representation of the currency code. "USD"

decimal The decimal separator. "."

firstDayOfWeek The first day of the week, where 1 is Sunday. 1

grouping The grouping separator. ","

isEasternNameStyle Specifies if a name is based on eastern style, for false

example, last name first name
[middle] [suffix].

labelForToday The label for the Today link on the date picker. “Today”

language The language code based on the language locale. "en", "de", "zh"

langLocale The locale ID. “en_US”, “en_GB”

nameOfMonths The full and short names of the calendar months { fullName: “January”, shortName: “Jan” }

nameOfWeekdays The full and short names of the calendar weeks { fullName: “Sunday”, shortName: “SUN” }

timezone The time zone ID. "America/Los_Angeles"

timezoneFileName The hyphenated name based on the time zone ID. “America-Los_Angeles”

userLocaleCountry The country based on the current user’s locale “US”

userLocaleLang The language based on the current user’s locale “en”

variant The vendor and browser-specific code. "WIN", "MAC", "POSIX"

Number and Date Formatting

The framework’s number and date formatting are based on Java’s DecimalFormat and DateFormat classes.

Attribute Description Sample Value

currencyformat The currency format. "¤#,##0.00;(¤#,##0.00)"
¤ represents the currency sign, which is replaced
by the currency symbol.

dateFormat The date format. "MMM d, yyyy"

datetimeFormat The date time format. "MMM d, yyyy h:mm:ss a"

numberformat The number format. "#,##0.###"

# represents a digit, the comma is a placeholder for
the grouping separator, and the period is a

35
Creating Components Expression Evaluation

Attribute Description Sample Value

placeholder for the decimal separator. Zero (0)
replaces # to represent trailing zeros.

percentformat The percentage format. "#,##0%"

timeFormat The time format. "h:mm:ss a"

zero The character for the zero digit. “0”

Example: This example shows how to retrieve different $Locale attributes.

Component source
<aura:component>
{!$Locale.language}
{!$Locale.timezone}
{!$Locale.numberFormat}
{!$Locale.currencyFormat}
</aura:component>

Similarly, you can check locale information in a client-side controller using $A.get().
({
checkDevice: function(component) {
var locale = $A.get("$Locale.language");
alert("You are using " + locale);
}
})

SEE ALSO:
Localization

Adding Custom Global Value Providers

Add a custom global value provider by implementing the GlobalValueProviderAdapter interface.

SEE ALSO:
Value Providers
Overriding Default Adapters
Default Adapters

Expression Evaluation
Expressions are evaluated much the same way that expressions in JavaScript or other programming languages are evaluated.
Operators are a subset of those available in JavaScript, and evaluation order and precedence are generally the same as JavaScript.
Parentheses enable you to ensure a specific evaluation order. What you may find surprising about expressions is how often they are
evaluated. The framework notices when things change, and trigger re-rendering of any components that are affected. Dependencies

36
Creating Components Expression Operators Reference

are handled automatically. This is one of the fundamental benefits of the framework. It knows when to re-render something on the page.
When a component is re-rendered, any expressions it uses will be re-evaluated.

Action Methods
Expressions are also used to provide action methods for user interface events: onclick, onhover, and any other component
attributes beginning with "on".
Action methods must be assigned to attributes using an expression, for example {!c.theAction}. This expression assigns a
reference to the controller function that handles the action.
Assigning action methods via expressions allows you to assign them conditionally, based on the state of the application or user interface.
For more information, see Conditional Expressions on page 27.
<aura:component>
<aura:attribute name="liked" type="Boolean" default="true"/>
<lightning:button aura:id="likeBtn"
label="{!(v.liked) ? 'Like It' : 'Unlike It'}"
onclick="{!(v.liked) ? c.likeIt : c.unlikeIt}"
/>
</aura:component>

This button will show "Like It" for items that have not yet been liked, and clicking it will call the likeIt action method. Then the
component will re-render, and the opposite user interface display and method assignment will be in place. Clicking a second time will
unlike the item, and so on.

Note: The example demonstrates how attributes can help you control the state of a button. To create a button that toggles
between states, we recommend using the lightning:buttonStateful component.

Expression Operators Reference

The expression language supports operators to enable you to create more complex expressions.

Arithmetic Operators
Expressions based on arithmetic operators result in numerical values.

Operator Usage Description

+ 1 + 1 Add two numbers.

- 2 - 1 Subtract one number from the other.

* 2 * 2 Multiply two numbers.

/ 4 / 2 Divide one number by the other.

% 5 % 2 Return the integer remainder of dividing the first number by the

second.

- -v.exp Unary operator. Reverses the sign of the succeeding number. For
example if the value of expenses is 100, then -expenses
is -100.

37
Creating Components Expression Operators Reference

Numeric Literals
Literal Usage Description
Integer 2 Integers are numbers without a decimal point or exponent.

Float 3.14 Numbers with a decimal point, or numbers with an exponent.

-1.1e10

Null null A literal null number. Matches the explicit null value and numbers
with an undefined value.

String Operators
Expressions based on string operators result in string values.

Operator Usage Description

+ 'Title: ' + v.note.title Concatenates two strings together.

String Literals
String literals must be enclosed in single quotation marks 'like this'.

Literal Usage Description

string 'hello world' Literal strings must be enclosed in single quotation marks. Double quotation marks
are reserved for enclosing attribute values, and must be escaped in strings.

\<escape> '\n' Whitespace characters:

• \t (tab)
• \n (newline)
• \r (carriage return)
Escaped characters:
• \" (literal ")
• \' (literal ')
• \\ (literal \)

Unicode '\u####' A Unicode code point. The # symbols are hexadecimal digits. A Unicode literal
requires four digits.

null null A literal null string. Matches the explicit null value and strings with an undefined
value.

38
Creating Components Expression Operators Reference

Comparison Operators
Expressions based on comparison operators result in a true or false value. For comparison purposes, numbers are treated as the
same type. In all other cases, comparisons check both value and type.

Operator Alternative Usage Description

== eq 1 == 1 Returns true if the operands are equal. This
1 == 1.0 comparison is valid for all data types.

1 eq 1 Warning: Don’t use the == operator for

objects, as opposed to basic types, such as
Note: Integer or String. For example,
undefined==null object1==object2 evaluates
evaluates to true. inconsistently on the client versus the server
and isn’t reliable.

!= ne 1 != 2 Returns true if the operands are not equal. This

1 != true comparison is valid for all data types.

1 != '1'
null != false
1 ne 2

< lt 1 < 2 Returns true if the first operand is numerically

1 lt 2 less than the second. You must escape the <
operator to &lt; to use it in component markup.
Alternatively, you can use the lt operator.

> gt 42 > 2 Returns true if the first operand is numerically

42 gt 2 greater than the second.

<= le 2 <= 42 Returns true if the first operand is numerically

2 le 42 less than or equal to the second. You must escape
the <= operator to &lt;= to use it in component
markup. Alternatively, you can use the le operator.

>= ge 42 >= 42 Returns true if the first operand is numerically

42 ge 42 greater than or equal to the second.

Logical Operators
Expressions based on logical operators result in a true or false value.

Operator Usage Description

&& isEnabled && Returns true if both operands are individually true. You must escape the && operator to
hasPermission &amp;&amp; to use it in component markup. Alternatively, you can use the and()
function and pass it two arguments. For example, and(isEnabled, hasPermission).

39
Creating Components Expression Functions Reference

Operator Usage Description

|| hasPermission Returns true if either operand is individually true.
|| isRequired

! !isRequired Unary operator. Returns true if the operand is false. This operator should not be confused
with the ! delimiter used to start an expression in {!. You can combine the expression
delimiter with this negation operator to return the logical negation of a value, for example,
{!!true} returns false.

Logical Literals
Logical values are never equivalent to non-logical values. That is, only true == true, and only false == false; 1 !=
true, and 0 != false, and null != false.

Literal Usage Description

true true A boolean true value.

false false A boolean false value.

Conditional Operator
There is only one conditional operator, the traditional ternary operator.

Operator Usage Description

? : (1 != 2) ? "Obviously" : "Black The operand before the ? operator is evaluated as
is White" a boolean. If true, the second operand is returned. If
false, the third operand is returned.

SEE ALSO:
Expression Functions Reference

Expression Functions Reference

The expression language contains math, string, array, comparison, boolean, and conditional functions. All functions are case-sensitive.

Math Functions
The math functions perform math operations on numbers. They take numerical arguments. The Corresponding Operator column lists
equivalent operators, if any.

Function Alternative Usage Description Corresponding

Operator
add concat add(1,2) Adds the first argument +
to the second.

40
Creating Components Expression Functions Reference

Function Alternative Usage Description Corresponding

Operator
sub subtract sub(10,2) Subtracts the second -
argument from the first.

mult multiply mult(2,10) Multiplies the first *

argument by the second.

div divide div(4,2) Divides the first argument /

by the second.

mod modulus mod(5,2) Returns the integer %

remainder resulting from
dividing the first
argument by the second.

abs abs(-5) Returns the absolute None

value of the argument:
the same number if the
argument is positive, and
the number without its
negative sign if the
number is negative. For
example, abs(-5) is
5.

neg negate neg(100) Reverses the sign of the - (unary)

argument. For example,
neg(100) is -100.

String Functions
Function Alternative Usage Description Corresponding
Operator
concat add concat('Hello ', Concatenates the two +
'world') arguments.
add('Walk ', 'the dog')

format format($Label.ns.labelName, Replaces any

v.myVal) parameter
placeholders with
Note: This function works for comma-separated
arguments of type String, attribute values.
Decimal, Double,
Integer, Long, Array,
String[], List, and Set.

41
Creating Components Expression Functions Reference

Function Alternative Usage Description Corresponding

Operator
join join(separator, subStr1, Joins the substrings
subStr2, subStrN) adding the separator
join(' ','class1',
String (first argument)
'class2', v.class)
between each
subsequent argument.

Label Functions
Function Usage Description
format format($Label.np.labelName, Outputs a label and updates it.
v.attribute1 , v.attribute2) Replaces any parameter
format($Label.np.hello, v.name)
placeholders with
comma-separated attribute values.
Supports ternary operators in
labels and attributes.

Informational Functions
Function Usage Description
length myArray.length Returns the length of an array or a string.

empty empty(v.attributeName) Returns true if the argument is empty. An empty

argument is undefined, null, an empty array, or an
Note: This function works for arguments
empty string. An object with no properties is not considered
of type String, Array, Object,
empty.
List, Map, or Set.
Tip: {! !empty(v.myArray)} evaluates
faster than {!v.myArray &&
v.myArray.length > 0} so we recommend
empty() to improve performance.
The $A.util.isEmpty() method in JavaScript is
equivalent to the empty() expression in markup.

Comparison Functions
Comparison functions take two number arguments and return true or false depending on the comparison result. The eq and
ne functions can also take other data types for their arguments, such as strings.

42
Creating Components Expression Functions Reference

Function Usage Description Corresponding

Operator
equals equals(1,1) Returns true if the specified arguments == or eq
are equal. The arguments can be any data
type.

notequals notequals(1,2) Returns true if the specified arguments != or ne

are not equal. The arguments can be any
data type.

lessthan lessthan(1,5) Returns true if the first argument is < or lt

numerically less than the second
argument.

greaterthan greaterthan(5,1) Returns true if the first argument is > or gt

numerically greater than the second
argument.

lessthanorequal lessthanorequal(1,2) Returns true if the first argument is <= or le

numerically less than or equal to the
second argument.

greaterthanorequal greaterthanorequal(2,1) Returns true if the first argument is >= or ge

numerically greather than or equal to the
second argument.

Boolean Functions
Boolean functions operate on Boolean arguments. They are equivalent to logical operators.

Function Usage Description Corresponding Operator

and and(isEnabled, Returns true if both &&
hasPermission) arguments are true.

or or(hasPermission, Returns true if either one of ||

hasVIPPass) the arguments is true.

not not(isNew) Returns true if the argument !

is false.

Conditional Function
Function Usage Description Corresponding Operator
if if(isEnabled, Evaluates the first argument as ?: (ternary)
'Enabled', 'Not a boolean. If true, returns the
enabled') second argument. Otherwise,
returns the third argument.

43
Creating Components Using Labels

Using Labels
Labels are text that presents information about the user interface, such as in the header (1), input fields (2), or buttons (3). While you can
specify labels by providing text values in component markup, you can also access labels stored outside your code using the $Label
global value provider in expression syntax.

This section discusses how to use the $Label global value provider in these contexts:
• The label attribute in input components
• The format() expression function for dynamically populating placeholder values in labels
• The aura:label component for populating placeholder values with components or markup in labels
• The ui:label component for visual separation with the label’s corresponding input component

IN THIS SECTION:
$Label
Separating labels from source code makes it easier to translate and localize your applications. Use the $Label global value provider
to access labels stored outside your code.
Input Component Labels
A label describes the purpose of an input component. To set a label on an input component, use the label attribute.
Dynamically Populating Label Parameters
Output and update labels using the format() expression function.
Getting Labels in JavaScript
You can retrieve labels in JavaScript code. Your code performs optimally if the labels are statically defined and sent to the client
when the component is loaded.
Setting Label Values via a Parent Attribute
Setting label values via a parent attribute is useful if you want control over labels in child components.
Customizing your Label Implementation

44
Creating Components $Label

$Label
Separating labels from source code makes it easier to translate and localize your applications. Use the $Label global value provider
to access labels stored outside your code.
$Label doesn’t have a default implementation but the LocalizationAdapter interface assumes that a label has a two-part
name: a section name and a label name. This enables you to organize labels into sections with similar labels grouped together.
To customize the behavior of the $Label global value provider, see Customizing your Label Implementation on page 50.
Access a label using the dot notation, $Label.<section>.<labelName>; for example, {!$Label.SocialApp.YouLike}.
Each name must start with a letter or underscore so that the label can be accessed in an expression. For example,
{!$Label.1SocialApp.2YouLike} is not valid because the section and label name each start with a number.

SEE ALSO:
Localization

Input Component Labels

A label describes the purpose of an input component. To set a label on an input component, use the label attribute.
This example shows how to use labels using the label attribute on an input component.
<ui:inputNumber label="Pick a Number:" labelPosition="top" value="54" />

The label position can be hidden, top, right, or bottom. The default position is left.

Using $Label
Use the $Label global value provider to access labels stored in an external source. For example:
<lightning:input type="number" name="myNumber" label="{!$Label.Number.PickOne}" />

To output a label and dynamically update it, use the format() expression function. For example, if you have np.labelName set
to Hello {0}, the following expression returns Hello World if v.name is set to World.
{!format($Label.np.labelName, v.name)}

Separating Labels from Input Components

For design reasons, you might want a significant visual separation of an HTML <label> tag from its corresponding form element, In
such a scenario, use the ui:label component to bind the label to the input component using the local ID, aura:id, of the input
component.
This code sample shows how to bind a label using the aura:id of an input component.
<ui:label labelDisplay="false" for="myInput" label="My Input Text" />
<!-- HTML markup separating the label from the input component -->
<ui:inputText aura:id="myInput" value="Put your input here." />

Note: We recommend that you use lightning:input component, which provides an accessible label for the input
component.

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Creating Components Dynamically Populating Label Parameters

To associate the ui:label tag with the input component, the for attribute in ui:label is set to the same value as the aura:id
in the input component.
Note that setting labelDisplay="false" in ui:label hides the label from view but still exposes it to screen readers. For
more information, refer to the ui:label component reference documentation.

SEE ALSO:
Dynamically Populating Label Parameters
Getting Labels in JavaScript
Supporting Accessibility
Java Models

Dynamically Populating Label Parameters

Output and update labels using the format() expression function.
You can provide a string with placeholders, which are replaced by the substitution values at runtime.
Add as many parameters as you need. The parameters are numbered and are zero-based. For example, if you have three parameters,
they will be named {0}, {1}, and {2}, and they will be substituted in the order they're specified.
Let's look at a custom label, $Label.mySection.myLabel, with a value of Hello {0} and {1}, where $Label is the
global value provider that accesses your labels.
This expression dynamically populates the placeholder parameters with the values of the supplied attributes.
{!format($Label.mySection.myLabel, v.attribute1, v.attribute2)}

The label is automatically refreshed if one of the attribute values changes.

The format() expression is more concise and preferred to the equivalent <aura:label> markup:
<aura:label value="{!$Label.mySection.myLabel}">
{!v.attribute1}
{!v.attribute2}
</aura:label>

Note: Always use the $Label global value provider to reference a label with placeholder parameters. You can't set a string
with placeholder parameters as the first argument for format(). For example, this syntax doesn't work:
{!format('Hello {0}', v.name)}

Use this expression instead.

{!format($Label.mySection.salutation, v.name)}

where $Label.mySection.salutation is set to Hello {0}.

Populating Parameters with Components or Markup

You must use <aura:label> instead of format() to populate parameters with component or markup. For example:
<aura:label value="{!$Label.message.hello}">
<ui:button>{!v.name}</ui:button>
</aura:label>

46
Creating Components Getting Labels in JavaScript

This example shows how to include a link in a label by substituting the {0} parameter with the embedded ui:outputURL
component. The $Label.MySection.LinkLabel label is defined as Label with link: {0}.
<aura:label value="{!$Label.MySection.LinkLabel}">
<ui:outputURL value="http://www.salesforce.com" label="Test Link"/>
</aura:label>

This example is similar to the previous one except that the label value is hard-coded and doesn't use the label provider.
<aura:component>
<aura:label value="Label with link: {0}">
<ui:outputURL value="http://www.salesforce.com" label="Test Link"/>
</aura:label>
</aura:component>

This is equivalent to embedding the HTML anchor tag:

<aura:label value="{!$Label.MySection.LinkLabel}">
<a href="http://www.salesforce.com">Test Link</a>
</aura:label>

Embedding aura:label in Another Component

You can use an aura:label component with parameter substitutions as the label of another component. For example, you can use
an aura:label component as the label of a ui:button component. Set the labelDisplay attribute to false so that
the label attribute won't be rendered. The embedded label in aura:label is displayed instead.
This example embeds the label component from the previous example inside a ui:button component. The button label is taken
from this embedded label component, which in turn contains an ui:outputURL component in its body for substituting a parameter
with a link. $Label.MySection.LinkLabel is defined as Label with link: {0}.
<ui:button labelDisplay="false" label="{!$Label.MySection.LinkLabel}">
<aura:label value="{!$Label.MySection.LinkLabel}">
<ui:outputURL value="http://www.salesforce.com" label="Test Link"/>
</aura:label>
</ui:button>

Note: Setting the labelDisplay attribute to false hides the label provided by the label attribute on the ui:button
component from view, but makes it available to screen readers.
The next example uses a hard-coded label value rather than a value from the label provider. The {0} placeholder is replaced by the
Test Link label at runtime.

<aura:component>
<ui:button labelDisplay="false" label="Label with link: {0}">
<aura:label value="Label with link: {0}">
<ui:outputURL value="http://www.salesforce.com" label="Test Link"/>
</aura:label>
</ui:button>
</aura:component>

Getting Labels in JavaScript

You can retrieve labels in JavaScript code. Your code performs optimally if the labels are statically defined and sent to the client when
the component is loaded.

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Creating Components Getting Labels in JavaScript

Static Labels
Static labels are defined in one string, such as "$Label.c.task_mode_today". The framework parses static labels in markup
or JavaScript code and sends the labels to the client when the component is loaded. A server trip isn’t required to resolve the label.
Use $A.get() to retrieve static labels in JavaScript code. For example:
var staticLabel = $A.get("$Label.c.task_mode_today");
component.set("v.mylabel", staticLabel);

Dynamic Labels
$A.get(labelReference) must be able to resolve the label reference at compile time, so that the label values can be sent to
the client along with the component definition.
If you must defer label resolution until runtime, you can dynamically create labels in JavaScript code. This technique can be useful when
you need to use a label, but which specific label isn’t known until runtime.
// Assume the day variable is dynamically generated
// earlier in the code
// THIS CODE WON’T WORK
var dynamicLabel = $A.get("$Label.c." + day);

If the label is already known on the client, $A.get() displays the label. If the value is not known, an empty string is displayed in PROD
mode, or a placeholder value showing the label key is displayed in all other modes.
Using $A.get()with a label that can't be determined at runtime means that dynamicLabel is an empty string, and won’t be
updated to the retrieved value. Since the label, "$Label.c." + day, is dynamically generated, the framework can’t parse it or
send it to the client when the component is requested.
There are a few alternative approaches to using $A.get() so that you can work with dynamically generated labels.
If your component uses a known set of dynamically constructed labels, you can avoid a server roundtrip for the labels by adding a
reference to the labels in a JavaScript resource. The framework sends these labels to the client when the component is requested. For
example, if your component dynamically generates $Label.c.task_mode_today and $Label.c.task_mode_tomorrow
label keys, you can add references to the labels in a comment in a JavaScript file, such as a client-side controller or helper.
// hints to ensure labels are preloaded
// $Label.c.task_mode_today
// $Label.c.task_mode_tomorrow

If your code dynamically generates many labels, this approach doesn’t scale well.
If you don’t want to add comment hints for all the potential labels, the alternative is to use $A.getReference(). This approach
comes with the added cost of a server trip to retrieve the label value.
This example dynamically constructs the label value by calling $A.getReference() and updates a tempLabelAttr component
attribute with the retrieved label.
var labelSubStr = "task_mode_today";
var labelReference = $A.getReference("$Label.c." + labelSubStr);
cmp.set("v.tempLabelAttr", labelReference);
var dynamicLabel = cmp.get("v.tempLabelAttr");

$A.getReference() returns a reference to the label. This isn’t a string, and you shouldn’t treat it like one. You never get a string
label directly back from $A.getReference().

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Creating Components Setting Label Values via a Parent Attribute

Instead, use the returned reference to set a component’s attribute value. Our code does this in cmp.set("v.tempLabelAttr",
labelReference);.
When the label value is asynchronously returned from the server, the attribute value is automatically updated as it’s a reference. The
component is rerendered and the label value displays.

Note: Our code sets dynamicLabel = cmp.get("v.tempLabelAttr") immediately after getting the reference.
This code displays an empty string until the label value is returned from the server. If you don’t want that behavior, use a comment
hint to ensure that the label is sent to the client without requiring a later server trip.

SEE ALSO:
Using JavaScript
Input Component Labels
Dynamically Populating Label Parameters
Customizing your Label Implementation
Modes Reference

Setting Label Values via a Parent Attribute

Setting label values via a parent attribute is useful if you want control over labels in child components.
Let’s say that you have a container component, which contains another component, inner.cmp. You want to set a label value in
inner.cmp via an attribute on the container component. This can be done by specifying the attribute type and default value. You
must set a default value in the parent attribute if you are setting a label on an inner component, as shown in the following example.
This is the container component, which contains a default value My Label for the _label attribute .
<aura:component>
<aura:attribute name="_label"
type="String"
default="My Label"/>
<lightning:button label="Set Label" aura:id="button1" onclick="{!c.setLabel}"/>
<auradocs:inner aura:id="inner" label="{!v._label}"/>
</aura:component>

This inner component contains a text area component and a label attribute that’s set by the container component.
<aura:component>
<aura:attribute name="label" type="String"/>
<lightning:textarea aura:id="textarea"
name="myTextarea"
label="{!v.label}"/>
</aura:component>

This client-side controller action updates the label value.

({
setLabel:function(cmp) {
cmp.set("v._label", 'new label');
}
})

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Creating Components Customizing your Label Implementation

When the component is initialized, you’ll see a button and a text area with the label My Label. When the button in the container
component is clicked, the setLabel action updates the label value in the inner component. This action finds the label attribute
and sets its value to new label.

SEE ALSO:
Input Component Labels
Component Attributes

Customizing your Label Implementation

You can customize where your app reads labels from by overriding the default label adapter. Your label adapter implementation
encapsulates the details of finding and returning labels defined outside the application code. Typically, labels are defined separately
from the source code to make localization of labels easier.
To provide a label adapter implementation, implement the LocalizationAdapter interface with the following two methods.
public class MyLocalizationAdapterImpl implements LocalizationAdapter {

@Override
public String getLabel(String section, String name, Object... params) {
// Return specified label.
}

@Override
public boolean labelExists(String section, String name) {
// Return true if the label exists; otherwise false.
}

The getLabel method contains the implementation for finding the specified label and returning it. Here is a description of its
parameters:

Parameter Description
String section The section in the label definition file where the label is defined. This assumes your label name has two
parts (section.name). This parameter can be null depending on your label system implementation.

String name The label name.

Object params A list of parameter values for substitution on the server. This parameter can be null if parameter
substitution is done on the client.

The labelExists method indicates whether the specified label is defined or not. Its method parameters are identical to the first
two parameters for getLabel.

SEE ALSO:
Plugging in Custom Code with Adapters
Input Component Labels
Dynamically Populating Label Parameters

50
Creating Components Localization

Localization
The framework provides client-side localization support on input and output components.
The components retrieve the browser's locale information and display the output components accordingly.
The following example shows how you can override the default timezone attribute. The output displays the time in the format
hh:mm by default.

<aura:component>
<ui:outputDateTime value="2013-10-07T00:17:08.997Z" timezone="Europe/Berlin" />
</aura:component>

The component renders as Oct 7, 2013 2:17:08 AM.

To customize the date and time formatting, we recommend using lightning:formattedDateTime. This example sets the
date and time using the init handler.
<aura:component>
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
<aura:attribute name="datetime" type="DateTime"/>
<lightning:formattedDateTime value="{!v.datetime}" timeZone="Europe/Berlin"
year="numeric" month="short" day="2-digit" hour="2-digit"

minute="2-digit" second="2-digit"/>
</aura:component>

({
doInit : function(component, event, helper) {
var date = new Date();
component.set("v.datetime", date)
}
})

This example creates a JavaScript Date instance, which is rendered in the format MMM DD, YYYY HH:MM:SS AM.
Although the output for this example is similar to <ui:outputDateTime value="{!v.datetime}"
timezone="Europe/Berlin" />, the attributes on lightning:formattedDateTime enable you to control formatting
at a granular level. For example, you can display the date using the MM/DD/YYYY format.
<lightning:formattedDateTime value="{!v.datetime}" timeZone="Europe/Berlin" year="numeric"
month="numeric" day="numeric"/>

Additionally, you can use the global value provider, $Locale, to obtain the locale information. By default, the framework uses the
browser's locale, but it can be configured to use others through the global value provider.

SEE ALSO:
Formatting Dates in JavaScript

Providing Component Documentation

Component documentation helps others understand and use your components.
You can provide two types of component reference documentation:

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Creating Components Providing Component Documentation

• Documentation definition (DocDef): Full documentation on a component, including a description, sample code, and a reference to
an example. DocDef supports extensive HTML markup and is useful for describing what a component is and what it does.
• Inline descriptions: Text-only descriptions, typically one or two sentences, set via the description attribute in a tag.
To provide a DocDef, create a .auradoc file in the component bundle and use the <aura:documentation> tag to wrap your
documentation. The following example shows the documentation definition (DocDef) for the ui:button component.

Note: DocDef is currently supported for components and applications. Events and interfaces support inline descriptions only.

<aura:documentation>
<aura:description>
<p>
A <code>ui:button</code> component represents a button element that executes an action
defined by a controller.
Clicking the button triggers the client-side controller method set for the
<code>press</code> event.
The button can be created in several ways.
</p>
<p>
A text-only button has only the required <code>label</code> attribute set on it.
To create a button with both image and text, use the <code>label</code> attribute and
add styles for the button.
</p>
<p>The visual appearance of buttons is highly configurable, as are text and accessibility
attributes.</p>

<!--More markup here, such as <pre> for code samples-->

<p>The markup for a button with text and image results in the following HTML. </p>

<pre>
<button class="default uiBlock uiButton" accesskey type="button">
<img class="icon bLeft" alt="Find" src="path/to/img">
<span class="label bBody truncate" dir="ltr">Find</span>
</button>
</pre>

</aura:description>
<aura:example name="buttonExample" ref="uiExamples:buttonExample" label="Using ui:button">

<p>This example shows a button that displays the input value you enter.</p>
</aura:example>
<aura:example name="buttonSecondExample" ref="uiExamples:buttonSecondExample"
label="Customizing ui:button">
<p>This example shows a customized <code>ui:button</code> component.</p>
</aura:example>
</aura:documentation>

A documentation definition contains these tags.

Tag Description
<aura:documentation> The top-level definition of the DocDef

<aura:description> Describes the component using extensive HTML markup. To include code samples in the
description, use the <pre> tag, which renders as a code block. Code entered in the <pre> tag

52
Creating Components Providing Component Documentation

Tag Description
must be escaped. For example, escape <aura:component> by entering
&lt;aura:component&gt;.

<aura:example> References an example that demonstrates how the component is used. Supports extensive HTML
markup, which displays as text preceding the visual output and example component source. The
example is displayed as interactive output. Multiple examples are supported and should be wrapped
in individual <aura:example> tags.
• name: The API name of the example
• ref: The reference to the example component in the format
<namespace:exampleComponent>
• label: The label of the title

Providing an Example Component

Recall that the DocDef includes a reference to an example component. The example component is rendered as an interactive demo in
the component reference documentation when it’s wired up using aura:example.
<aura:example name="buttonExample" ref="uiExamples:buttonExample" label="Using ui:button">

The following is an example component that demonstrates how ui:button can be used.

<!--The uiExamples:buttonExample example component -->

<aura:component>
<ui:inputText aura:id="name" label="Enter Name:" placeholder="Your Name" />
<ui:button aura:id="button" buttonTitle="Click to see what you put into the field"
class="button" label="Click me" press="{!c.getInput}" />
<ui:outputText aura:id="outName" value="" class="text" />
</aura:component>

Providing Inline Descriptions

Inline descriptions provide a brief overview of what an element is about. HTML markup is not supported in inline descriptions. These
tags support inline descriptions via the description attribute.

Tag Example
<aura:component> <aura:component description="Represents a button element">

<aura:attribute> <aura:attribute name="label" type="String" description="The

text to be displayed inside the button."/>

<aura:event> <aura:event type="COMPONENT" description="Indicates that a

keyboard key has been pressed and released"/>

<aura:interface> <aura:interface description="A common interface for date

components"/>

53
Creating Components Working with UI Components

Tag Example
<aura:registerEvent> <aura:registerEvent name="keydown" type="ui:keydown"
description="Indicates that a key is pressed"/>

SEE ALSO:
Reference

Working with UI Components

The framework provides common user interface components in the ui namespace. All of these components extend either
aura:component or a child component of aura:component. aura:component is an abstract component that provides
a default rendering implementation. User interface components such as ui:input and ui:output provide easy handling of
common user interface events like keyboard and mouse interactions. Each component can be styled and extended accordingly.

Note: If you are looking for components that apply the Lightning Design System styling, consider using the base lightning
components instead.

Complex, Interactive Components

The following components contain one or more sub-components and are interactive.

Type Key Components Description

Autocomplete ui:autocomplete An input field that suggests a list of values as you type

Carousel ui:carousel A list of pages that can be swiped horizontally

ui:carouselPage A scrollable page in a ui:carousel component

Dialog ui:panel A modal or non-modal overlay

ui:panelManager2 A component that instantiates and handles panels

Message ui:message A message notification of varying severity levels

Menu ui:menu A drop-down list with a trigger that controls its visibility. This
component extends ui:popup.

ui:menuList A list of menu items

ui:actionMenuItem A menu item that triggers an action

ui:checkboxMenuItem A menu item that supports multiple selection and can be used to
trigger an action

ui:radioMenuItem A menu item that supports single selection and can be used to
trigger an action

ui:menuItemSeparator A visual separator for menu items

ui:menuItem An abstract and extensible component for menu items in a

ui:menuList component

54
Creating Components Working with UI Components

Type Key Components Description

ui:menuTrigger A trigger that expands and collapses a menu

ui:menuTriggerLink A link that triggers a dropdown menu. This component extends

ui:menuTrigger

Popup ui:popup A popup with a trigger that controls its visibility. Used by ui:menu

ui:popupTarget A container that’s displayed in response to a trigger.

ui:popupTrigger A trigger that expands and collapses a menu.

Tabset ui:tab A single tab in a ui:tabset component

ui:tabBar A list wrapper for tabs in a ui:tabset component

ui:tabItem A single tab that’s rendered by a ui:tabBar component

ui:tabset A set of tabs that’s displayed in an unordered list

Input Control Components

The following components are interactive, for example, like buttons and checkboxes.

Type Key Components Description

Button ui:button An actionable button that can be pressed or clicked

Checkbox ui:inputCheckbox A selectable option that supports multiple selections

ui:outputCheckbox Displays a read-only value of the checkbox

Radio button ui:inputRadio A selectable option that supports only a single selection

Drop-down List ui:inputSelect A drop-down list with options

ui:inputSelectOption An option in a ui:inputSelect component

ui:inputSelectOptionGroup

Visual Components
The following components provides informative cues, for example, like error messages and loading spinners.

Type Key Components Description

Field-level error ui:inputDefaultError An error message that is displayed when an error occurs

Input Label ui:label A text label that binds to an input component

Layout ui:block A horizontal layout that provides two or three columns

ui:vbox A vertical layout that provides two or three rows

List ui:list A collection of items that can be iterated over and displayed

55
Creating Components Working with UI Components

Type Key Components Description

Spinner ui:spinner A loading spinner

Field Components
The following components enables you to enter or display values.

Type Key Components Description

Currency ui:inputCurrency An input field for entering currency

ui:outputCurrency Displays currency in a default or specified format

Email ui:inputEmail An input field for entering an email address

ui:outputEmail Displays a clickable email address

Date and time ui:inputDate An input field for entering a date

ui:inputDateTime An input field for entering a date and time

ui:outputDate Displays a date in the default or specified format

ui:outputDateTime Displays a date and time in the default or specified format

Password ui:inputSecret An input field for entering secret text

Percentage ui:inputPercent An input field for entering a percentage

ui:outputPercent Displays a percentage in the default or specified format

Phone Number ui:inputPhone An input field for entering a telephone number

ui:outputPhone Displays a phone number

Number ui:inputNumber An input field for entering a numerical value

ui:outputNumber Displays a number

Range ui:inputRange An input field for entering a value within a range

Rich Text ui:inputRichText An input field for entering rich text

ui:outputRichText Displays rich text

Search ui:inputSearch An input field for entering a search string

Text ui:inputText An input field for entering a single line of text

ui:outputText Displays text

Text Area ui:inputTextArea An input field for entering multiple lines of text

ui:outputTextArea Displays a read-only text area

URL ui:inputURL An input field for entering a URL

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Creating Components Event Handling in UI Components

Type Key Components Description

ui:outputURL Displays a clickable URL

SEE ALSO:
Using the UI Components
Creating Components
Component Bundles

Event Handling in UI Components

UI components provide easy handling of user interface events such as keyboard and mouse interactions. By listening to these events,
you can also bind values on UI input components using the updateon attribute, such that the values update when those events are
fired.
Capture a UI event by defining its handler on the component. For example, you want to listen to the HTML DOM event, onblur, on a
ui:inputTextArea component.

<ui:inputTextArea aura:id="textarea" value="My text area" label="Type something"

blur="{!c.handleBlur}" />

The blur="{!c.handleBlur}" listens to the onblur event and wires it to your client-side controller. When you trigger the
event, the following client-side controller handles the event.
handleBlur : function(cmp, event, helper){
var elem = cmp.find("textarea").getElement();
//do something else
}

These events are available to any components that implement the ui:visible and ui:uiEvents interfaces. The ui:visible
interface provides event registration for mouse events and attributes that defines a component’s class and label. The ui:uiEvents
interface provides event registration for form events, such as blur and focus.
For all available events on all components, refer to the Reference Doc App on page 323.

Value Binding for Browser Events

Any changes to the UI are reflected in the component attribute, and any change in that attribute is propagated to the UI. When you
load the component, the value of the input elements are initialized to those of the component attributes. Any changes to the user input
causes the value of the component variable to be updated. For example, a ui:inputText component can contain a value that’s
bound to a component attribute, and the ui:outputText component is bound to the same component attribute. The
ui:inputText component listens to the onkeyup browser event and updates the corresponding component attribute values.

<aura:attribute name="first" type="String" default="John"/>

<aura:attribute name="last" type="String" default="Doe"/>

<ui:inputText label="First Name" value="{!v.first}" updateOn="keyup"/>

<ui:inputText label="Last Name" value="{!v.last}" updateOn="keyup"/>

<!-- Returns "John Doe" -->

<ui:outputText value="{!v.first +' '+ v.last}"/>

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Creating Components Using the UI Components

The next example takes in numerical inputs and returns the sum of those numbers. The ui:inputNumber component listens to
the onkeyup browser event. When the value in this component changes on the keyup event, the value in the ui:outputNumber
component is updated as well, and returns the sum of the two values.
<aura:attribute name="number1" type="integer" default="1"/>
<aura:attribute name="number2" type="integer" default="2"/>

<ui:inputNumber label="Number 1" value="{!v.number1}" updateOn="keyup" />

<ui:inputNumber label="Number 2" value="{!v.number2}" updateOn="keyup" />

<!-- Adds the numbers and returns the sum -->

<ui:outputNumber value="{!(v.number1 * 1) + (v.number2 * 1)}"/>

Note: The input fields return a string value and must be properly handled to accommodate numerical values. In this example,
both values are multiplied by 1 to obtain their numerical equivalents.

Using the UI Components

Users interact with your app through input elements to select or enter values. Components such as ui:inputText and
ui:inputCheckbox correspond to common input elements. These components simplify event handling for user interface events.

Note: For all available component attributes and events, see the component reference at
http://<myServer>/auradocs/reference.app .
To use input components in your own custom component, add them to your .cmp or .app file. This example is a basic set up of a
text field and button. The aura:id attribute defines a unique ID that enables you to reference the component from your JavaScript
code using cmp.find("myID");.
<ui:inputText label="Name" aura:id="name" placeholder="First, Last"/>
<ui:outputText aura:id="nameOutput" value=""/>
<ui:button aura:id="outputButton" label="Submit" press="{!c.getInput}"/>

Note: All text fields must specify the label attribute to provide a textual label of the field. If you must hide the label from view,
set labelClass="assistiveText" to make the label available to assistive technologies.
The ui:outputText component acts as a placeholder for the output value of its corresponding ui:inputText component.
The value in the ui:outputText component can be set with the following client-side controller action.
getInput : function(cmp, event) {
var fullName = cmp.find("name").get("v.value");
var outName = cmp.find("nameOutput");
outName.set("v.value", fullName);
}

The following example is similar to the previous, but uses value binding without a client-side controller. The ui:outputText
component reflects the latest value on the ui:inputText component when the onkeyup browser event is fired.
<aura:attribute name="first" type="String" default="John"/>
<aura:attribute name="last" type="String" default="Doe"/>

<ui:inputText label="First Name" value="{!v.first}" updateOn="keyup"/>

<ui:inputText label="Last Name" value="{!v.last}" updateOn="keyup"/>

<!-- Returns "John Doe" -->

<ui:outputText value="{!v.first +' '+ v.last}"/>

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Creating Components Using the UI Components

Date and Time Fields

Date and time fields provide client-side localization, date picker support, and support for common keyboard and mouse events. If you
want to render the output from these field components, use the respective ui:output components. For example, to render the
output for the ui:inputDate component, use ui:outputDate.
Date and Time fields are represented by the following components.

Field Type Description Related Components

Date An input field for entering a date of type ui:inputDate
text. Provide a date picker by setting ui:outputDate
displayDatePicker="true". Web
apps running on mobiles and tablets use an
input field of type date.

Date and Time An input field for entering a date and time ui:inputDateTime
of type text. Provide a date picker and ui:outputDateTime
time picker by setting
displayDatePicker="true". On
desktop, the date and time fields display as
two separate fields. The time picker displays
a list of time in 30-minute increments. Web
apps running on mobiles and tablets use an
input field of type datetime-local.

Using the Date and Time Fields

This is a basic set up of a date field with a date picker.
<ui:inputDate aura:id="dateField" label="Birthday" value="2000-01-01"
displayDatePicker="true"/>

This example results in the following HTML.

<div class="uiInput uiInputDate uiInput--default uiInput--input uiInput--datetime">
<label class="uiLabel-left form-element__label uiLabel">
<span>Birthday</span>
</label>
<form class="form--stacked form-element">
<input placeholder="MMM d, yyyy" type="text">
<a class="datePicker-openIcon display" aria-haspopup="true">
<span class="assistiveText">Date Picker</span>
</a>
<a class="clearIcon hide">
<span class="assistiveText">Clear Button</span>
</a>
</form>
</div>
<div class="DESKTOP uiDatePicker--default uiDatePicker">
<!--Date picker set to visible when icon is clicked-->
</div>

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Styling Your Date and Time Fields

You can style the appearance of your date and time field and output in the CSS file of your component.
The following example provides styles to a ui:inputDateTime component with the myStyle selector.
<!-- Component markup -->
<ui:inputDateTime class="myStyle" label="Date" displayDatePicker="true"/>

/* CSS */
.THIS .myStyle {
border: 1px solid #dce4ec;
border-radius: 4px;
}

SEE ALSO:
Input Component Labels
Handling Events with Client-Side Controllers
Localization
CSS in Components

Number Fields
Number fields can contain a numerical value. They support client-side formatting, localization, and common keyboard and mouse events.
If you want to render the output from these field components, use the respective ui:output components. For example, to render
the output for the ui:inputNumber component, use ui:outputNumber.
Number fields are represented by the following components.

Type Related Components Description

Number ui:inputNumber An input field for entering a numerical value

ui:outputNumber Displays a number

Currency ui:inputCurrency An input field for entering currency

ui:outputCurrency Displays currency

Percentage ui:inputPercent An input field for entering a numerical

ui:outputPercent percentage value.

Range ui:inputRange A slider for numerical input.

Using the Number Fields

This example shows a basic set up of a percentage number field, which displays 50% in the field.
<ui:label label="Discount" for="discountField"/>
<ui:inputPercent aura:id="discountField" value="0.5"/>

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This is a basic set up of a range input, with the min and max attributes.
<ui:label label="Quantity" for="qtyField"/>
<ui:inputRange aura:id="qtyField" min="1" max="10"/>

ui:label provides a text label for the corresponding field.

These examples result in the following HTML.
<label for="globalId" class="uiLabel"><span>Discount</span></label>
<iput aria-describedby max="99999999999999" step="1" placeholder type="text"
min="-99999999999999" id="globalId" class="uiInput uiInputText uiInputNumber uiInputPercent">

<label for="globalId" class="uiLabel"><span>Quantity</span></label>

<input max="10" step="1" type="range" min="1" id="globalId" class="uiInput uiInputText
uiInputNumber uiInputRange">

Returning a Valid Number

The value of the ui:inputNumber component expects a valid number and won’t work with commas. If you want to include commas,
use type="Integer" instead of type="String".
This example returns 100,000.
<aura:attribute name="number" type="Integer" default="100,000"/>
<ui:inputNumber label="Number" value="{#v.number}"/>

Note: {#v.number} is an unbound expression. This means that any change to the value attribute in ui:inputNumber
doesn’t propagate back to affect the value of the number attribute in the parent component. For more information, see Data
Binding Between Components on page 27.
This example also returns 100,000.
<aura:attribute name="number" type="String" default="100000"/>
<ui:inputNumber label="Number" value="{#v.number}"/>

Formatting and Localizing the Number Fields

The format attribute determines the format of the number input. The Locale default format is used if none is provided. The following
code is a basic set up of a number field, which displays 10,000.00 based on the provided format attribute.
<ui:inputNumber label="Cost" aura:id="costField" format="#,##0,000.00#" value="10000"/>

The following code is a basic set up of a percentage field with client-side formatting, which displays 14.000% based on the provided
format attribute.

<ui:outputPercent label="Growth" aura:id="pField" value="0.14" format=".000%"/>

The following code is a basic set up of a currency field with localization, which displays £10.00 based on the provided
currencySymbol and format attributes. You can also set the currencyCode attribute with an ISO 4217 currency code, such
as USD or GBP.
<ui:outputCurrency value="10" currencySymbol="£" format="¤.00" />

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Number and Currency Shortcuts

Users can enter the shortcuts k, m, b, t to indicate thousands, millions, billions, or trillions in ui:inputNumber and
ui:inputCurrency components. This feature is available in Lightning Experience, and all versions of the Salesforce mobile app.

Styling Your Number Fields

You can style the appearance of your number field and output. In the CSS file of your component, add the corresponding class selectors.
The following class selectors provide styles to the string rendering of the numbers. For example, to style the ui:inputCurrency
component, use .THIS .uiInputCurrency, or .THIS.uiInputCurrency if it’s a top-level element.
The following example provides styles to a ui:inputNumber component with the myStyle selector.
<!-- Component markup -->
<ui:inputNumber class="myStyle" label="Amount" placeholder="0" />

/* CSS */
.THIS .myStyle {
border: 1px solid #dce4ec;
border-radius: 4px;
}

SEE ALSO:
Input Component Labels
Handling Events with Client-Side Controllers
Localization
CSS in Components

Text Fields
A text field can contain alphanumerical characters and special characters. They provide common keyboard and mouse events. If you
want to render the output from these field components, use the respective ui:output components. For example, to render the
output for the ui:inputPhone component, use ui:outputPhone.
Text fields are represented by the following components.

Type Related Components Description

Email ui:inputEmail An input field for entering an email address

ui:outputEmail Displays a clickable email address

Password ui:inputSecret An input field for entering secret text

Phone Number ui:inputPhone An input field for entering a telephone

number

ui:outputPhone Displays a clickable phone number

Rich Text ui:inputRichText An input field for entering rich text

ui:outputRichText Displays rich text

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Creating Components Using the UI Components

Type Related Components Description

Search ui:inputSearch An input field for entering a search term.

Text ui:inputText An input field for entering single line of text

ui:outputText Displays text

Text Area ui:inputTextArea An input field for entering multiple lines of

text

ui:outputTextArea Displays a read-only text area

URL ui:inputURL An input field for entering a URL

ui:outputURL Displays a clickable URL

Using the Text Fields

Text fields are typically used in a form. For example, this is a basic set up of an email field.
<ui:inputEmail aura:id="email" label="Email" placeholder="abc@email.com"/>

This example results in the following HTML.

<div class="uiInput uiInputEmail uiInput--default uiInput--input">
<label class="uiLabel-left form-element__label uiLabel">
<span>Email</span>
</label>
<input placeholder="abc@email.com" type="email" class="input">
</div>

Providing Auto-complete Suggestions in Text Fields

Auto-complete is available with the ui:autocomplete component, which uses a text or text area of its own. To use a text area, set
the inputType="inputTextArea". The default is inputText.

Styling Your Text Fields

You can style the appearance of your text field and output. In the CSS file of your component, add the corresponding class selectors.
For example, to style the ui:inputPhone component, use .THIS .uiInputPhone, or .THIS.uiInputPhone if it’s a
top-level element.
The following example provides styles to a ui:inputText component with the myStyle selector.
<!-- Component markup-->
<ui:inputText class="myStyle" label="Name"/>

/* CSS */
.THIS .myStyle {
border: 1px solid #dce4ec;

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border-radius: 4px;
}

SEE ALSO:
Rich Text Fields
Input Component Labels
Handling Events with Client-Side Controllers
Localization
CSS in Components

Rich Text Fields

ui:inputRichText is an input field for entering rich text. The following code shows a basic implementation of this component,
which is rendered as a text area and button. A button click runs the client-side controller action that returns the input value in a
ui:outputRichText component. In this case, the value returns “Aura” in bold, and “input rich text demo” in red.

<!--Rich text demo-->

<ui:inputRichText isRichText="false" aura:id="inputRT" label="Rich Text Demo"
cols="50" rows="5" value="&lt;b&gt;Aura&lt;/b&gt;, &lt;span style='color:red'&gt;input
rich text demo&lt;/span&gt;"/>
<ui:button aura:id="outputButton"
buttonTitle="Click to see what you put into the rich text field"
label="Display" press="{!c.getInput}"/>
<ui:outputRichText aura:id="outputRT" value=" "/>

/*Client-side controller*/
getInput : function(cmp) {
var userInput = cmp.find("inputRT").get("v.value");
var output = cmp.find("outputRT");
output.set("v.value", userInput);
}

In this demo, the isRichText="false" attribute replaces the component with the ui:inputTextArea component. The
WYSIWYG rich text editor is provided when this attribute is not set, as shown below.

The width and height of the rich text editor are independent of those on the ui:inputTextArea component. To set the width
and height of the component when you set isRichText="false", use the cols and rows attributes. Otherwise, use the
width and height attributes.

SEE ALSO:
Text Fields

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Creating Components Using the UI Components

Checkboxes
Checkboxes are clickable and actionable, and they can be presented in a group for multiple selection. You can create a checkbox with
ui:inputCheckbox, which inherits the behavior and events from ui:input. The value and disabled attributes control
the state of a checkbox, and events such as click and change determine its behavior. Events must be used separately on each
checkbox.
Here are several basic ways to set up a checkbox.
Checked
To select the checkbox, set value="true". Alternatively, value can take in a value from a model.
<ui:inputCheckbox value="true"/>

<!--Initializing the component-->

<ui:inputCheckbox aura:id="inCheckbox" value="{!m.checked}"/>

//Initializing with a model

public Boolean getChecked() {
return true;
}

The model is in a Java class specified by the model attribute on the aura:component tag.
Disabled State
<ui:inputCheckbox disabled="true" label="Select" />

The previous example results in the following HTML.

<div class="uiInput uiInputCheckbox uiInput--default uiInput--checkbox">
<label class="uiLabel-left form-element__label uiLabel"
for="globalId"><span>Select</span></label>
<input disabled="disabled" type="checkbox id="globalId">

Working with Events

Common events for ui:inputCheckbox include the click and change events. For example, click="{!c.done}" calls
the client-side controller action with the function name, done.
The following code crosses out the checkbox item.
<!--The checkbox-->
<ui:inputCheckbox label="Cross this out" click="{!c.crossout}" class="line" />

/*The controller action*/

crossout : function(cmp, event){
var cmpSource = event.getSource();
$A.util.toggleClass(cmpSource, "done");
}

SEE ALSO:
Java Models
Handling Events with Client-Side Controllers
CSS in Components

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Radio Buttons
Radio buttons are clickable and actionable, and they can only be individually selected when presented in a group. You can create a radio
button with ui:inputRadio, which inherits the behavior and events from ui:input. The value and disabled attributes
control the state of a radio button, and events such as click and change determine its behavior. Events must be used separately
on each radio button.
If you want to use radio buttons in a menu, use ui:radioMenuItem instead.
Here are several basic ways to set up a radio button.
Selected
To select the radio button, set value="true".
<ui:inputRadio value="true" label="Select?"/>

Disabled State
<ui:inputRadio label="Select" disabled="true"/>

The previous example results in the following HTML.

<div class="uiInput uiInputRadio uiInput--default uiInput--radio">
<label class="uiLabel-left form-element__label uiLabel"
for="globalId"><span>Select</span></label>
<input type="radio" id="globalId">

Providing Labels using An Attribute

You can also initialize the label values using an attribute. This example uses an attribute to populate the radio button labels and wire
them up to a client-side controller action when the radio button is selected or deselected.
<!--c:labelsAttribute-->
<aura:component>
<aura:attribute name="stages" type="String[]" default="Any,Open,Closed,Closed,Closed
Won"/>
<aura:iteration items="{#v.stages}" var="stage">
<ui:inputRadio label="{#stage}" change="{!c.doSomething}"/>
</aura:iteration>
</aura:component>

Note: {#v.stages} and {#stage} are unbound expressions. This means that any change to the value of the items
attribute in aura:iteration or the label attribute in ui:inputRadio don’t propagate back to affect the value of
the stages attribute in c:labelsAttribute. For more information, see Data Binding Between Components on page 27.

Working with Events

Common events for ui:inputRadio include the click and change events. For example, click="{!c.showItem}"
calls the client-side controller action with the fuction name, showItem.
The following code updates the CSS class of a component when the radio button is clicked.
<!--The radio button-->
<ui:inputRadio click="{!c.showItem}" label="Show Item"/>

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/* The controller action */

showItem : function(cmp, event) {
var myCmp = cmp.find('myCmp');
$A.util.toggleClass(myCmp, "cssClass");
}

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

Buttons
A button is clickable and actionable, providing a textual label, an image, or both. You can create a button in three different ways:
• Text-only Button
<ui:button label="Find" />

• Image-only Button
<ui:button iconImgSrc="/auraFW/resources/aura/images/search.png" label="Find"
labelDisplay="false"/>

• Button with Text and Image

<ui:button label="Find" iconImgSrc="/auraFW/resources/aura/images/search.png"/>

HTML Rendering
The markup for a button with text and image results in the following HTML.
<button class="button uiButton--default uiButton" accesskey type="button">
<img class="icon bLeft" alt="Find" src="path/to/img">
<span class="label bBody truncate" dir="ltr">Find</span>
</button>

Working with Click Events

The press event on the ui:button component is fired when the user clicks the button. In the following example,
press="{!c.getInput}" calls the client-side controller action with the function name, getInput, which outputs the input
text value.
<aura:component>
<ui:inputText aura:id="name" label="Enter Name:" placeholder="Your Name" />
<ui:button aura:id="button" label="Click me" press="{!c.getInput}"/>
<ui:outputText aura:id="outName" value="" class="text"/>
</aura:component>

/* Client-side controller */
({
getInput : function(cmp, evt) {
var myName = cmp.find("name").get("v.value");

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var myText = cmp.find("outName");

var greet = "Hi, " + myName;
myText.set("v.value", greet);
}

Controlling Propagation
To control propagation of DOM events, use the stopPropagation attribute. This example toggles propagation on a ui:button
component.
<aura:component>
<aura:attribute name="propagation" type="Boolean" default="false"/>
<div onclick="{!c.handleWrapperClick}">
<ui:button press="{!c.handleClick}" stopPropagation="{!v.propagation}" label="Aura
Button"/>
</div><br/>
Propagation status: {! v.propagation ? 'OFF' : 'ON'}<br/>
<ui:button press="{!c.togglePropagation} label="Toggle Propagation"/>
</aura:component>

/* Client-side controller */
({
handleClick: function(cmp, event, helper) {
console.log(event);
},
handleWrapperClick: function(cmp, event, helper) {
alert('Click propagated to wrapper');
},
togglePropagation: function(cmp, event, helper) {
cmp.set('v.propagation', !cmp.get('v.propagation'));
}
})

Styling Your Buttons

The ui:button component is customizable with regular CSS styling. In the CSS file of your component, add the following class
selector.
.THIS.uiButton {
margin-left: 20px;
}

Note that no space is added in the .THIS.uiButton selector if your button component is a top-level element.

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To override the styling for all ui:button components in your app, in the CSS file of your app, add the following class selector.
.THIS .uiButton {
margin-left: 20px;
}

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components
Which Button Was Pressed?

Drop-down Lists
Drop-down lists display a dropdown menu with options you can select.
Both single and multiple selections are supported. You can create a drop-down list using ui:inputSelect, which inherits the
behavior and events from ui:input.
Here are a few basic ways to set up a drop-down list.
For multiple selections, set the multiple attribute to true.
Single Selection
<ui:inputSelect>
<ui:inputSelectOption text="Red"/>
<ui:inputSelectOption text="Green" value="true"/>
<ui:inputSelectOption text="Blue"/>
</ui:inputSelect>

Multiple Selection
<ui:inputSelect multiple="true">
<ui:inputSelectOption text="All Primary" label="All Contacts"/>
<ui:inputSelectOption text="All Primary" label="All Primary"/>
<ui:inputSelectOption text="All Secondary" label="All Secondary"/>
</ui:inputSelect>

Each option is represented by ui:inputSelectOption. The default selected value is specified by value="true" on the
option.

Note: v.value represents the option’s HTML selected attribute, and v.text represents the option’s HTML value
attribute.

Generating Options with aura:iteration

You can use aura:iteration to iterate over a list of items to generate options. This example iterates over a list of items and
conditionally renders the options.
<aura:attribute name="contacts" type="String[]" default="All Contacts,Others"/>
<ui:inputSelect>
<aura:iteration items="{!v.contacts}" var="contact">
<aura:if isTrue="{!contact == 'All Contacts'}">
<ui:inputSelectOption text="{!contact}" label="{!contact}"/>
<aura:set attribute="else">

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<ui:inputSelectOption text="All Primary" label="All Primary"/>

<ui:inputSelectOption text="All Secondary" label="All Secondary"/>
</aura:set>
</aura:if>
</aura:iteration>
</ui:inputSelect>

Generating Options Dynamically

Generate the options dynamically on component initialization.
<aura:component>
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
<ui:inputSelect label="Select me:" class="dynamic" aura:id="InputSelectDynamic"/>
</aura:component>

The following client-side controller generates options using v.options on the ui:inputSelect component by creating the
opts object with several parameters. v.options takes in the list of objects and converts them into list options. Although the sample
code generates the options during initialization, the list of options can be modified anytime when you manipulate the list in v.options.
The component automatically updates itself and rerenders with the new options.
({
doInit : function(cmp) {
var opts = [
{ class: "optionClass", label: "Option1", value: "opt1"},
{ class: "optionClass", label: "Option2", value: "opt2" },
{ class: "optionClass", label: "Option3", value: "opt3" }

];
cmp.find("InputSelectDynamic").set("v.options", opts);
}
})

Note: class is a reserved word that might not work with older versions of Internet Explorer. We recommend using "class"
with double quotes.
The list options support these parameters.

Parameter Type Description

class String The CSS class for the option.

disabled Boolean Indicates whether the option is disabled.

label String The label of the option to display on the

user interface.

selected Boolean Indicates whether the option is selected.

value String Required. The value of the option.

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Using Options On Multiple Lists

If you’re reusing the same set of options on multiple drop-down lists, use different attributes for each set of options. Otherwise, selecting
a different option in one list also updates other list options bound to the same attribute.
<aura:attribute name="options1" type="String" />
<aura:attribute name="options2" type="String" />
<ui:inputSelect aura:id="Select1" label="Select1" options="{!v.options1}" />
<ui:inputSelect aura:id="Select2" label="Select2" options="{!v.options2}" />

Working with Events

Common events for ui:inputSelect include the change and click events. For example,
change="{!c.onSelectChange}" calls the client-side controller action with the function name, onSelectChange, when
a user changes a selection.

Styling Your Field-level Errors

The ui:inputSelect component is customizable with regular CSS styling. The following CSS sample adds a fixed width to the
drop-down menu.
.THIS.uiInputSelect {
width: 200px;
height: 100px;
}

Alternatively, use the class attribute to specify your own CSS class.

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

Field-level Errors
Field-level errors are displayed when an input validation error occurs on the field. Input components in the lightning namespace
display a default error message when an error condition is met. For input components in the ui namespace, the framework creates a
default error component, ui:inputDefaultError, which provides basic events such as click and mouseover. See Validating
Fields for more information.
Alternatively, you can use ui:message for field-level errors by toggling visibility of the message when an error condition is met. See
Dynamically Showing or Hiding Markup for more information.

Working with Events

Common events for ui:message include the click and mouseover events. For example, click="{!c.revalidate}"
calls the client-side controller action with the function name, revalidate, when a user clicks the error message.

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

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Creating Components Using the UI Components

Menus
A menu is a drop-down list with a trigger that controls its visibility. You must provide the trigger and list of menu items. The dropdown
menu and its menu items are hidden by default. You can change this by setting the visible attribute on the ui:menuList
component to true. The menu items are shown only when you click the ui:menuTriggerLink component.
This example creates a menu with several items.
<ui:menu>
<ui:menuTriggerLink aura:id="trigger" label="Opportunity Status"/>
<ui:menuList class="actionMenu" aura:id="actionMenu">
<ui:actionMenuItem aura:id="item2" label="Open"
click="{!c.updateTriggerLabel}"/>
<ui:actionMenuItem aura:id="item3" label="Closed"
click="{!c.updateTriggerLabel}"/>
<ui:actionMenuItem aura:id="item4" label="Closed Won"
click="{!c.updateTriggerLabel}"/>
</ui:menuList>
</ui:menu>

The following components are nested in ui:menu.

Component Description
ui:menu A drop-down list with a trigger that controls its visibility

ui:menuList A list of menu items

ui:actionMenuItem A menu item that triggers an action

ui:checkboxMenuItem A menu item that supports multiple selection and can be used to
trigger an action

ui:radioMenuItem A menu item that supports single selection and can be used to
trigger an action

ui:menuItemSeparator A visual separator for menu items

ui:menuItem An abstract and extensible component for menu items in a

ui:menuList component

ui:menuTrigger A trigger that expands and collapses a menu

ui:menuTriggerLink A link that triggers a dropdown menu. This component extends

ui:menuTrigger

Horizontal Layouts
ui:block provides a horizontal layout for your components. It extends aura:component and is an actionable component. It is
useful for laying out your labels, fields, and buttons or any groups of components in a row.
Here is a basic set up of a horizontal layout. The following sample code creates a horizontal view of an image, text field, and a button.
The ui:inputText component renders in between the left and right attributes.
<ui:block>
<aura:set attribute="left">

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<ui:image src="/auraFW/resources/aura/images/search.png" alt="bLeft" />

</aura:set>
<aura:set attribute="right">
<ui:button label="Submit"/>
</aura:set>
<ui:inputText label="Text" labelPosition="hidden" />
</ui:block>

Working with Events

Common events for ui:block include the click and mouseover events. For example, click="{!c.enable}" calls the
client-side controller action with the function name, enable, when a user clicks anywhere in the layout.

Styling Your Horizontal Layouts

ui:block is customizable with regular CSS styling. The output is rendered in div tags with the bLeft, bRight, and bBody
classes.

The following CSS class styles the bLeft class on the ui:block.
.THIS.uiBlock .bLeft { //CSS declaration }

Alternatively, use the class attribute to specify your own CSS class.

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

Vertical Layouts
ui:vbox provides a vertical layout for your components. It extends aura:component and is an actionable component. It is useful
for laying out groups of components vertically on a page.
Here is a basic set up of a vertical layout. The following sample code creates a vertical view of a header, body, and footer. The body of
the component renders in between the north and south attributes.
<ui:vbox>
<aura:set attribute="north">
<div id="header">Header</div>
</aura:set>
<aura:set attribute="south">
<div id="footer">Footer</div>
</aura:set>
body
</ui:vbox>

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Creating Components Using the UI Components

Working with Events

Common events for ui:vbox include the click and mouseover events. For example, click="{!c.enable}" calls the
client-side controller action with the fuction name, enable, when a user clicks anywhere in the layout.

Styling Your Vertical Layouts

ui:vbox is customizable with regular CSS styling. Given the above example, the output is rendered in <div id="header"
class="uiVbox"> and <div id="footer" class="uiVbox"> tags, with the footer rendered in the bottom.

The following CSS class styles the header element in the north attribute.
.THIS #header { //CSS declaration }

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

Working with Auto-Complete

ui:autocomplete displays suggestions as users type in a text field. Data for this component is provided by a server-side model.
This component provides its own text field and text area component. The default is a text field but you can change it to a text area by
setting inputType="inputTextArea".
Here is a basic set up of the auto-complete component with a default input text field.
<ui:autocomplete aura:id="autoComplete" optionVar="row"
matchDone="{!c.handleMatchDone}"
inputChange="{!c.handleInputChange}"
selectListOption="{!c.handleSelectOption}">
<aura:set attribute="dataProvider">
<demo:dataProvider/>
</aura:set>
<aura:set attribute="listOption">

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<ui:autocompleteOption label="{!row.label}" keyword="{!row.keyword}"

value="{!row.value}" visible="{!row.visible}"/>
</aura:set>
</ui:autocomplete>

Working with Events

Common events for ui:autocomplete include the fetchData, inputChange, matchDone, and selectListOption
events. The behaviors for these events can be configured as desired.
fetchData
Fire the fetchData event if you want to fetch data through the data provider. For example, you can fire this event in the
inputChange event when the input value changes. The ui:autocomplete component automatically matches text on
the new data.
inputChange
Use the inputChange event to handle an input value change. Get the new value with event.getParam("value"). The
following code handles a text match on existing data.
var matchEvt = acCmp.get("e.matchText");
matchEvt.setParams({
keyword: event.getParam("value")
});
matchEvt.fire();

matchDone
Use the matchDone event to handle when a text matching has completed, regardless if a match has occurred. You can retrieve
the number of matches with event.getParam("size").
selectListOption
Use the selectListOption event to handle when a list option is selected. Get the options with
event.getParam("option");. This event is fired by the ui:autocompleteList component when a list option is
selected.

Providing Data to the Auto-complete Component

In the basic set up above, demo:dataProvider provides the list of data to be displayed as suggestions when a text match occurs.
demo:dataProvider extends ui:dataProvider and takes in a server-side model.
The following code is a sample data provider for the ui:autocomplete component.
<aura:component extends="ui:dataProvider"
model="java://org.auraframework.impl.java.model.TestJavaModel">
<aura:attribute name="dataType" type="String"/>
</aura:component>

In the client-side controller or helper function of your data provider, fire the onchange event on the parent ui:dataProvider
component. This event handles any data changes on the list.
var data = component.get("m.listOfData");
var dataProvider = component.getConcreteComponent();
//Fire the onchange event in the ui:dataProvider component
this.fireDataChangeEvent(dataProvider, data);

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Creating Components Using the UI Components

See the data provider at aura/src/test/components/uitest/testAutocompleteDataProvider in the GitHub

repo.
To learn how the data provider is retrieving data from the model, see the server-side model at
/aura-impl/src/test/java/org/auraframework/impl/java/model/TestJavaModel.java in the GitHub
repo.

Styling Your Auto-complete Component

The ui:autocomplete component is customizable with regular CSS styling. For example, if you're using the default text field
component provided by ui:autocomplete, you can use the following CSS selector.
.THIS.uiInputText {
//CSS declaration
}

If you're using the default text area component provided by ui:autocomplete, change the CSS selector to
.THIS.uiInputTextArea. Alternatively, use the class attribute to specify your own CSS class.

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components
Client-Side Runtime Binding of Components

Creating Lists
You can create lists in three different ways, using aura:iteration, ui:list, or ui:infiniteList. aura:iteration
is used for simple lists and can take in data from a model.
ui:list and ui:infiniteList provide a paging interface to navigate lists. ui:list can be used for more robust list
implementations that retrieves and display more data as necessary, with a data provider and a template for each list item. Additionally,
use ui:infiniteList if you want a robust list implementation similar to ui:list, but with a handler that enables you to
retrieve and display more data when the user reaches the bottom of the list.
Here is a basic set up of the ui:list component with a required data provider and template.
<ui:list itemVar="item">
<aura:set attribute="dataProvider">
<auradev:testDataProvider />
</aura:set>
<aura:set attribute="header">
Item List
</aura:set>
<aura:set attribute="itemTemplate">
<auradocs:demoListTemplate label="{!item.label}" />
</aura:set>
</ui:list>

itemVar is a required attribute that is used to iterate over the items provided by the item template. In the above example,
{!item.label} iterates over the items provided by the data provider and displays the labels.

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Creating Components Using the UI Components

The sample template, auradocs:demoListTemplate is as follows. This template is a row of text generated by the data provider.
<aura:component>
<aura:attribute name="label" type="String"/>
<div class="row">
{!v.label}
</div>
</aura:component>

Working with List Events

ui:list and ui:infiniteList inherits from ui:abstractList. Common events for ui:list include user interface
events like click events, and list-specific events like refresh and triggerDataProvider.
refresh
The refresh event handles a list data refresh and fires the triggerDataProvider event. You can fire the refresh
event by using the following sample code in your client-side controller action.
var listData = cmp.find("listData");
listData.get("e.refresh").fire();

showMore
The showMore event in ui:infiniteList handles the fetching of your data and displays it. This event fires the
triggerDataProvider event as well.
triggerDataProvider
ThetriggerDataProvider event triggers the providing of data from a data provider. It is also run during component
initialization and refresh. For example, you can use this event if you want to retrieve more data in a ui:infiniteList component.
cmp.set("v.currentPage", targetPage);
var listData = component.find("listData");
listData.get("e.triggerDataProvider").fire();

Providing Data to the List Component

In the basic set up above, auradocs:demoDataProvider provides the list of data to the ui:list component.
auradocs:demoDataProvider extends ui:dataProvider and takes in a server-side model.
The following code is the sample data provider, auradocs:demoDataProvider.
<aura:component extends="ui:dataProvider"
model="java://org.auraframework.component.auradev.TestDataProviderModel"
controller="java://org.auraframework.component.auradev.TestDataProviderController"
description="A data provider for ui:list">
<aura:handler name="provide" action="{!c.provide}"/>
</aura:component>

The provide event is fired on initialization by the parent ui:abstractList component. You can customize the provide
event in your client-side controller. For example, the following code shows a sample provide helper function for a data provider.
var dataProvider = component.getConcreteComponent();
var action = dataProvider.get("c.getItems");

//Set the parameters for this action

action.setParams({

77
Creating Components Working with the Flow Lightning Component

"currentPage": dataProvider.get("v.currentPage"),
"pageSize": dataProvider.get("v.pageSize")
//Other ui:list or ui:infiniteList parameters
});

//Set the action callback

action.setCallback(this, function(response) {
var state = response.getState();
if (state === "SUCCESS") {
var result = response.getReturnValue();
this.fireDataChangeEvent(dataProvider, result);
}
});
$A.enqueueAction(action);

Note: See the data provider at aura-components/src/main/components/auradocs/demoDataProvider/

in the GitHub repo.
To learn how the data provider is retrieving data from the model, see the server-side model at
aura-impl/src/main/java/org/auraframework/component/auradev/TestDataProviderModel.java.

Styling Your List Component

The ui:list component is customizable with regular CSS styling. For example, the sample template code above has <div
class="row">. To apply CSS, you can use the following CSS selector in the template component.

.THIS .row{
//CSS declaration
}

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components

Working with the Flow Lightning Component

Once you embed a flow in a Lightning component, use JavaScript and Apex code to configure the flow at run time. For example, pass
values into the flow or to control what happens when the flow finishes. lightning:flow supports only flows of type Flow and
Autolaunched Flow.
A flow is an application, built with Visual Workflow, that collects, updates, edits, and creates Salesforce information.
To embed a flow in your Lightning component, add the <lightning:flow> component to it.
<aura:component>
<aura:handler name="init" value="{!this}" action="{!c.init}" />
<lightning:flow aura:id="flowData" />
</aura:component>

({
init : function (component) {
// Find the component whose aura:id is "flowData"

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Creating Components Set Flow Variable Values from a Lightning Component

var flow = component.find("flowData");

// In that component, start your flow. Reference the flow's Unique Name.
flow.startFlow("myFlow");
},
})

Note: When a user opens a page that has a flow component, such as Lightning App Builder or an active Lightning page, the flow
runs when the page loads. Make sure that the flow doesn’t perform any actions – such as create or delete records – before the
first screen.

IN THIS SECTION:
Set Flow Variable Values from a Lightning Component
When you embed a flow in a Lightning component, give the flow more context by initializing its variables, sObject variables, collection
variables, or sObject collection variables. In the component's controller, create a list of maps, then pass that list to the startFlow
method.
Get Flow Variable Values to a Lightning Component
Flow variable values can be displayed or referenced in a Lightning component. Once you’ve embedded your flow in a custom
Lightning component, use the onstatuschange action to get values from the flow's output variables. Output variables are
returned as an array.
Control a Flow’s Finish Behavior in a Lightning Component
By default, when a flow user clicks Finish, the component starts a new interview and the user sees the first screen of the flow again.
However, you can shape what happens when the flow finishes by using the onstatuschange action. To redirect to another
page, use one of the force:navigateTo* events such as force:navigateToObjectHome or
force:navigateToUrl.
Resume a Flow Interview from a Lightning Component
By default, users can resume their paused interviews from the Paused Interviews component on their home page in Salesforce
Classic. If you want to customize how and where users can resume their interviews, pass the interview ID into the resumeFlow
method in your JavaScript controller.

Set Flow Variable Values from a Lightning Component

When you embed a flow in a Lightning component, give the flow more context by initializing its variables, sObject variables, collection
variables, or sObject collection variables. In the component's controller, create a list of maps, then pass that list to the startFlow method.

Note: You can set variables only at the beginning of an interview, and the variables you set must allow input access. For each
flow variable, input access is controlled by:
• The Input/Output Type variable field in the Cloud Flow Designer
• The isInput field on FlowVariable in the Metadata API
If you reference a variable that doesn’t allow input access, attempts to set the variable are ignored.

For each variable you set, provide the variable's name, type, and value. For type, use the flow data type.

Flow Variable Type Valid Values

Type
Text String String value or equivalent expression

Number Number Numeric value or equivalent expression

79
Creating Components Set Flow Variable Values from a Lightning Component

Flow Variable Type Valid Values

Type
Currency Currency Numeric value or equivalent expression

Boolean Boolean • True values: true, 1, or equivalent expression

• False values: false, 0, or equivalent expression

Picklist Picklist String value or equivalent expression

Multi-Select Picklist Multipicklist String value or equivalent expression

Date Date "YYYY-MM-DD" or equivalent expression

Date/Time DateTime "YYYY-MM-DDThh:mm:ssZ" or equivalent expression

sObject SObject Map of key-value pairs or equivalent expression.

{
name : "varName",
type : "flowDataType",
value : valueToSet
},
{
name : "varName",
type : "flowDataType",
value : [ value1, value2]
}, ...

Example: This JavaScript controller sets values for a number variable, a date collection variable, and a couple of sObject variables.
({
init : function (component) {
// Find the component whose aura:id is "flowData"
var flow = component.find("flowData");
var inputVariables = [
{ name : "numVar", type : "Number", value: 30 },
{ name : "dateColl", type : "String", value: [ "2016-10-27", "2017-08-01" ]
},
// Sets values for fields in the account sObject variable. Id uses the
// value of the component's accountId attribute. Rating uses a string.
{ name : "account", type : "SObject", value: {
"Id" : component.get("v.accountId"),
"Rating" : "Warm"
}
},
// Set the contact sObject variable to the value of the component's contact

// attribute. We're assuming the attribute contains the entire sObject for
// a contact record.
{ name : "contact", type : "SObject", value: component.get("v.contact") }
},
];

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Creating Components Set Flow Variable Values from a Lightning Component

flow.startFlow("myFlow", inputVariables);
}
})

Example: Here's an example of a component that gets an account via an Apex controller. The Apex controller passes the data
to the flow's sObject variable through the JavaScript controller.
<aura:component controller="AccountController" >
<aura:attribute name="account" type="Account" />
<aura:handler name="init" value="{!this}" action="{!c.init}"/>
<lightning:flow aura:id="flowData"/>
</aura:component>

public with sharing class AccountController {

@AuraEnabled
public static Account getAccount() {
return [SELECT Id, Name, LastModifiedDate FROM Account LIMIT 1];
}
}

({
init : function (component) {
// Create action to find an account
var action = component.get("c.getAccount");

// Add callback behavior for when response is received

action.setCallback(this, function(response) {
if (state === "SUCCESS") {
// Pass the account data into the component's account attribute
component.set("v.account", response.getReturnValue());
// Find the component whose aura:id is "flowData"
var flow = component.find("flowData");
// Set the account sObject variable to the value of the component's
// account attribute.
var inputVariables = [
{
name : "account",
type : "SObject",
value: component.get("v.account")
}
];

// In the component whose aura:id is "flowData, start your flow

// and initialize the account sObject variable. Reference the flow's
// Unique Name.
flow.startFlow("myFlow", inputVariables);
}
else {
console.log("Failed to get account date.");
}
});

// Send action to be executed

$A.enqueueAction(action);

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Creating Components Get Flow Variable Values to a Lightning Component

}
})

Get Flow Variable Values to a Lightning Component

Flow variable values can be displayed or referenced in a Lightning component. Once you’ve embedded your flow in a custom Lightning
component, use the onstatuschange action to get values from the flow's output variables. Output variables are returned as an
array.

Note: The variable must allow output access. For each flow variable, output access is controlled by:
• The Input/Output Type variable field in the Cloud Flow Designer
• The isInput field on FlowVariable in the Metadata API
If you reference a variable that doesn’t allow output access, attempts to get the variable are ignored.

Example: This example uses the JavaScript controller to pass the flow's accountName and numberOfEmployees variables into
attributes on the component. Then, the component displays those values in output components.
<aura:component>
<aura:attribute name="accountName" type="String" />
<aura:attribute name="numberOfEmployees" type="Decimal" />

<p><lightning:formattedText value="{!v.accountName}" /></p>

<p><lightning:formattedNumber style="decimal" value="{!v.numberOfEmployees}" /></p>

<aura:handler name="init" value="{!this}" action="{!c.init}"/>

<lightning:flow aura:id="flowData" onstatuschange="{!c.handleStatusChange}" />
</aura:component>

({
init : function (component) {
// Find the component whose aura:id is "flowData"
var flow = component.find("flowData");
// In that component, start your flow. Reference the flow's Unique Name.
flow.startFlow("myFlow");
},

handleStatusChange : function (component, event) {

if(event.getParam("status") === "FINISHED") {
// Get the output variables and iterate over them
var outputVariables = event.getParam("outputVariables");
var outputVar;
for(var i = 0; i < outputVariables.length; i++) {
outputVar = outputVariables[i];
// Pass the values to the component's attributes
if(outputVar.name === "accountName") {
component.set("v.accountName", outputVar.value);
} else {
component.set("v.numberOfEmployees", outputVar.value);
}
}

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Creating Components Control a Flow’s Finish Behavior in a Lightning Component

}
},
})

Control a Flow’s Finish Behavior in a Lightning Component

By default, when a flow user clicks Finish, the component starts a new interview and the user sees the first screen of the flow again.
However, you can shape what happens when the flow finishes by using the onstatuschange action. To redirect to another page,
use one of the force:navigateTo* events such as force:navigateToObjectHome or force:navigateToUrl.

Note: To control what happens when an autolaunched flow finishes, check for the FINISHED_SCREEN status.

<aura:component access="global">
<aura:handler name="init" value="{!this}" action="{!c.init}" />
<lightning:flow aura:id="flowData" onstatuschange="{!c.handleStatusChange}" />
</aura:component>

// init function here

handleStatusChange : function (component, event) {
if(event.getParam("status") === "FINISHED") {
// Redirect to another page in Salesforce, or
// Redirect to a page outside of Salesforce, or
// Show a toast, or...
}
}

Example: This function redirects the user to a case created in the flow by using the force:navigateToSObject event.
handleStatusChange : function (component, event) {
if(event.getParam("status") === "FINISHED") {
var outputVariables = event.getParam("outputVariables");
var outputVar;
for(var i = 0; i < outputVariables.length; i++) {
outputVar = outputVariables[i];
if(outputVar.name === "redirect") {
var urlEvent = $A.get("e.force:navigateToSObject");
urlEvent.setParams({
"recordId": outputVar.value,
"isredirect": "true"
});
urlEvent.fire();
}
}
}
}

83
Creating Components Resume a Flow Interview from a Lightning Component

Resume a Flow Interview from a Lightning Component

By default, users can resume their paused interviews from the Paused Interviews component on their home page in Salesforce Classic.
If you want to customize how and where users can resume their interviews, pass the interview ID into the resumeFlow method in
your JavaScript controller.
({
init : function (component) {
// Find the component whose aura:id is "flowData"
var flow = component.find("flowData");

// In that component, resume a paused interview. Provide the method with

// the ID of the interview that you want to resume.
flow.resumeFlow("pausedInterviewId");
},
})

Example: This example show how you can resume an interview—or start a new one. When users click Survey Customer from
a contact record, the Lightning component does one of two things.
• If the user has any paused interviews for the Survey Customers flow, it resumes the first one.
• If the user doesn’t have any paused interviews for the Survey Customers flow, it starts a new one.
<aura:component controller="InterviewsController">
<aura:handler name="init" value="{!this}" action="{!c.init}" />
<lightning:flow aura:id="flowData" />
</aura:component>

This Apex controller performs a SOQL query to get a list of paused interviews. If nothing is returned from the query,
getPausedId() returns a null value, and the component starts a new interview. If at least one interview is returned from the
query, the component resumes the first interview in that list.
public class InterviewsController {
@AuraEnabled
public static String getPausedId() {
// Get the ID of the running user
String currentUser = UserInfo.getUserId();
// Find all of that user's paused interviews for the Survey customers flow
List<FlowInterview> interviews =
[ SELECT Id FROM FlowInterview
WHERE CreatedById = :currentUser AND InterviewLabel LIKE '%Survey
customers%'];

if (interviews == null || interviews.isEmpty()) {

return null; // early out
}
// Return the ID for the first interview in the list
return interviews.get(0).Id;
}
}

84
Creating Components Supporting Accessibility

If the JavaScript controller got an interview ID back from the Apex controller, the component resumes that interview. If the Apex
controller returned a null interview ID, the component starts a new interview.
({
init : function (component) {
//Create request for interview ID
var action = component.get("c.getPausedId");
action.setCallback(this, function(response) {
var interviewId = response.getReturnValue();
// Find the component whose aura:id is "flowData"
var flow = component.find("flowData");
// If an interview ID was returned, resume it in the component
// whose aura:id is "flowData".
if ( interviewId !== null ) {
flow.resumeFlow(interviewID);
}
// Otherwise, start a new interview in that component. Reference
// the flow's Unique Name.
else {
flow.startFlow("Survey_customers");
}
});
//Send request to be enqueued
$A.enqueueAction(action);
},
})

Supporting Accessibility
Components are created with accessibility in mind. This is also true for components that extend these components.
When customizing components, be careful in preserving code that ensures accessibility, such as the aria attributes.
Accessible software and assistive technology enable users with disabilities to use and interact with the products you build. Aura
components are created according to W3C specifications so that they work with common assistive technologies. While we always
recommend that you follow the WCAG Guidelines for accessibility when developing with Aura, this guide explains the accessibility
features that you can leverage when using components in the ui namespace.
In general, you can think of the components as either basic or complex, interactive components.
Basic Components
• ui:image — for images and icons
• ui:input — for input elements such as text fields and date fields
• ui:button — for input elements such as push buttons, radio buttons, and checkboxes
Complex, Interactive Components
• ui:autocomplete — for autocompleting dropdowns
• ui:carousel — for carousel interactions
• ui:tabset — for tab and tab panel interactions
• ui:datePicker — for calendar pickers
• ui:panel — for modal and non-modal overlays

85
Creating Components Supporting Accessibility

• ui:menu — for menus, dropdowns, and muttons

• ui:message — for displaying page updates to users and updating screen readers

Accessibility Testing
To check that a component’s HTML output is compliant with our accessibility validation, run $A.test.assertAccessible().
You can also run $A.devToolService.checkAccessibility() on a browser console. This tool checks the rendered DOM
elements to make sure that they pass Salesforce’s accessibility validation. Examples of this include image tags requiring an alt attribute,
active panels correctly setting the aria-hidden attribute, and input, select, and textarea tags having associated labels.
When using the tool, there are two outcomes: pass or fail. If the tool does not find any accessibility exceptions, it returns an empty string.
When the tool does find accessibility exceptions, it will include the accessibility rule that failed, the erroneous tag, and a stacktrace of
where it was found in the code.
To use these tests, you must have the Aura Framework loaded. The tests can be used in the console
($A.devToolService.checkAccessibility()), JSTEST ($A.test.assertAccessible()), or in a WebDriver test
(auraTestingUtil.assertAccessible()).
The tests look for these issues:
• Images without the alt attribute
• Anchor element without textual content
• input elements without an associated label
• Radio button groups not in a fieldset tag
• iframe or frame elements with empty title attribute
• fieldset element without a legend
• th element without a scope attribute
• head element with an empty title attribute
• Headings (H1, H2, etc.) increasing by more than one level at a time
• CSS color contrast ratio between text and background less than 4.5:1
Since Aura is a single page javascript application, the person writing the test will have to make sure to re-test when the DOM changes.
The person using the tool should place a check after the DOM has changed to ensure greater accessibility validation coverage.
The sections below include more information specific to different types of components.

IN THIS SECTION:
Button Labels
Carousels
Help and Error Messages
Audio Messages
Forms, Fields, and Labels
Images
Events
Dialog Overlays
Menus

86
Creating Components Button Labels

Resolving Accessibility Errors

Accessibility tests validate generated HTML markup and may return an error code followed by a message to help you resolve those
errors.

Button Labels
Buttons can appear with text only, an icon and text, or an icon without text. To create an accessible button, use lightning:button
and set a textual label using the label attribute.

Note: You can create accessible buttons using ui:button but they don’t come with Lightning Design System styling. We
recommend using lightning:button instead.
Button with text only:
<lightning:button label="Search" onclick="{!c.doSomething}"/>

Button with icon and text:

<lightning:button label="Download" iconName="utility:download" onclick="{!c.doSomething}"/>

Button with icon only:

<lightning:buttonIcon iconName="utility:settings" alternativeText="Settings"
onclick="{!c.doSomething}"/>

The alternativeText attribute provides a text label that’s hidden from view and available to assistive technology.
This example shows the HTML generated by lightning:button:
<!-- Good: using span/assistiveText to hide the label visually, but show it to screen
readers -->
<button>
::before
<span class="slds-assistive-text">Settings</span>
</button>

SEE ALSO:
Buttons

Carousels
The ui:carousel component displays a list of items horizontally where users can swipe through the list or click through the page
indicators.
If your code failed, check to make sure the page indicators are visible. If visible="false" is set on the
ui:carouselPageIndicatorItem, the page indicators will be hidden from view. Similarly, setting
continuousFlow="true" on ui:carousel hides the page indicators from view.

87
Creating Components Help and Error Messages

Help and Error Messages

Use the ariaDescribedby attribute to associate the help text or error message with a particular field. Let’s say you want to create
help text for ui:inputText.
<ui:inputText label="Contact Name" ariaDescribedby="contact" />
<ui:outputText aura:id="contact" value="This is an example of a help text." />

Using the input component to create and handle the ui:inputDefaultError component automatically applies the
ariaDescribedby attribute on the error messages. If you want to manually manage the action, you will need to make the connection
between the ui:inputDefaultError component and the associated output.
Your component should render like this example:
<!-- Good: aria-describedby is used to associate error message -->
<label for="fname">Contact name</label>
<input name="" type="text" id="fname" aria-describedby="msgid">
<ul class="uiInputDefaultError" id="msgid">
<li>Please enter the contact name</li>
</ul>

SEE ALSO:
Validating Fields

Audio Messages
To convey audio notifications, use the ui:message component, which has role="alert" set on the component by default.
The "alert" aria role will take any text inside the div and read it out loud to screen readers without any additional action by the
user.
<ui:message title="Error" severity="error" closable="true">
This is an error message.
</ui:message>

Forms, Fields, and Labels

Input components are designed to make it easy to assign labels to form fields. Labels build a programmatic relationship between a form
field and its textual label. You can assign a label in two ways. Use the label attribute on a component that extends ui:input or
use the ui:label component and bind it to the corresponding input component. When using a placeholder in an input component,
set the label attribute for accessibility.
Use lightning:input to create accessible input fields and forms. You can use lightning:textarea in preference to the
<textarea> tag for multi-line text input or lightning:select instead of the <select> tag.

<lightning:input name="myInput" label="Search" />

Designs often include form elements with placeholder text, but no visible label. A label is required for accessibility and can be hidden
visually. Set variant="label-hidden" to hide it from view but make the component accessible.
<lightning:input name="myInput" aura:id="myInput" value="Set your input value here."
variant="label-hidden"/>

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Creating Components Images

If your code fails, check the label element during component rendering. A label element should have the for attribute and match the
value of input control id attribute, OR the label should be wrapped around an input. Input controls include <input>, <textarea>,
and <select>.
Here’s an example of the HTML generated by lightning:input.
<!-- Good: using label/for= -->
<label for="fullname">Enter your full name:</label>
<input type="text" id="fullname" />

<!-- Good: --using implicit label>

<label>Enter your full name:
<input type="text" id="fullname"/>
</label>

SEE ALSO:
Using Labels

Images
For an image to be accessible, set an appropriate alternative text attribute. If your image is informational, or actionable as part of a
hyperlink, set the alt attribute to a descriptive alternative text. If the image is purely decorative, set imageType="decorative".
This generates a null alt attribute in the img tag.
<ui:image src="s.gif" imageType="informational" alt="Open Menu" />

<ui:image src="s.gif" imageType="decorative" />

When displaying an informational or actionable image via CSS, include the assistiveText class to provide an appropriate alternative
text.
<a class="like">
<span class="assistiveText">Like</span>
</a>

IN THIS SECTION:
Using Images

Using Images
To display images, use the ui:image component. The ui:image component automates common usages of the HTML <img>
tag, such as href linking and other attributes. Additionally, include the imageType attribute to show if the image is informational
or decorative. Use the title attribute for tooltips, especially for icons.

Informational Images
Informational images can provide information that may not be available in the text, such as a Like or Follow image. They are actionable
and can stand alone in a button or hyperlink. Include the alt tag to specify alternate text for the image, which is helpful if the user has
no access to the image.
<ui:image src="follow.png" imageType="informational" alt="follow" />

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Creating Components Events

If you use CSS to display an informational image, you must provide assistive text that will be put into the DOM, by using the
assistiveText class.

<div class="Following">
<span class="assistiveText">Following</span>
</div>

Decorative Images
Decorative images are images that can be removed without affecting the logic or content of the page. You don't need to specify assistive
text for decorative images.
<ui:image src="decoration.png" imageType="decorative" />

Code Samples
If your code failed, check to make sure you used the alt tag and the assistiveText class correctly.
Informational image code example:
alt tag:
<ui:image src="follow.png" imageType="informational" alt="follow" />
assistiveText class:
<div class="Following">
<span class="assistiveText">Following</span>
</div>

Decorative image code example:

<ui:image src="decoration.png" imageType="decorative" />

Events
Although you can attach an onclick event to any type of element, for accessibility, consider only applying this event to elements
that are actionable in HTML by default, such as <a>, <button>, or <input> tags in component markup. You can use an onclick
event on a <div> tag to prevent event bubbling of a click.

Dialog Overlays
The ui:panel component creates an overlay that lets users access additional information without leaving the current page. Modal
overlay requires the user to take an action or cancel the overlay to go back to the original page. Non-modal overlays offer useful information
but can be ignored by users.
To create a modal overlay, use panelType: 'modal', which locks keyboard focus inside the modal. autoFocus must be also
true for the component to be accessible. autoFocus is true by default. To create a non-modal overlay, set panelType: 'panel'
and users can just tab through. Fire the ui:createPanel event to create a modal or non-modal overlay.
$A.get('e.ui:createPanel').setParams({
panelType: 'modal',
visible: true,
panelConfig: {
title: 'Modal Header',
autoFocus: true,

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Creating Components Menus

body: body,
footer: footer
},
onCreate: function(panel){
//do something
}
}).fire();

ui:panel needs to have a title to meet accessibility standards, but it doesn’t have to be visible. Use titleDisplay: false
to hide the title, if desired.

Menus
A menu is a dropdown list with a trigger that controls its visibility. You must provide the trigger, which displays a text label, and a list of
menu items. The dropdown menu and its menu items are hidden by default. You can change this by setting the visible attribute
on the ui:menuList component to true. The menu items are shown only when you click the ui:menuTriggerLink
component.
This example code creates a menu with several items:
<ui:menu>
<ui:menuTriggerLink aura:id="trigger" label="Opportunity Status"/>
<ui:menuList class="actionMenu" aura:id="actionMenu">
<ui:actionMenuItem aura:id="item2" label="Open"
click="{!c.updateTriggerLabel}"/>
<ui:actionMenuItem aura:id="item3" label="Closed"
click="{!c.updateTriggerLabel}"/>
<ui:actionMenuItem aura:id="item4" label="Closed Won"
click="{!c.updateTriggerLabel}"/>
</ui:menuList>
</ui:menu>

Different menus achieve different goals. Make sure you use the right menu for the desired behavior. The three types of menus are:
Actions
Use the ui:actionMenuItem for items that create an action, like print, new, or save.
Radio button
If you want users to pick only one from a list several items, use ui:radioMenuItem.
Checkbox style
If users can pick multiple items from a list of several items, use ui:checkboxMenuItem. Checkboxes can also be used to turn
one item on or off.

Note: To create a dropdown menu with a trigger that’s a button, use lightning:buttonMenu instead.

Resolving Accessibility Errors

Accessibility tests validate generated HTML markup and may return an error code followed by a message to help you resolve those
errors.
The following errors flag accessibility issues in your components. Resolve these errors to ensure that your components are accessible.

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Creating Components Resolving Accessibility Errors

[A11Y_DOM_01] All image tags require the presence of the alt attribute
Informational images must have a description set on its alt attribute. If the image is decorative, set alt="". For more information,
see Images on page 89.
<!-- Informational image -->
<img src="admin.png" alt="admin image">

[A11Y_DOM_02] Labels are required for all input controls

A label element should have a for attribute and match the value of the id attribute on the input control, or the label should be
wrapped around the input. Input controls include <input>, <textarea> and <select>. For more information, see Forms,
Fields, and Labels on page 88.
<!-- Method 1: Use label/for -->
<label for="fullname">Enter your full name:</label>
<input type="text" id="fullname"/>

<!-- Method 2: Use an implicit label-->

<label>Enter your full name:
<input type="text" id="fullname"/>
</label>

[A11Y_DOM_03] Buttons must have non-empty text labels

When using ui:button, assign a non-empty string to the label attribute. For an icon-only button, use labelDisplay in
ui:button to hide the label text. For more information, see Button Labels on page 87.

<!-- Method 1: Use the alt attribute to provide a hidden label -->
<button>
<img src="enter_site.gif" alt="enter site"/>
</button>

<!-- Method 2: Use a span tag with assistiveText class to hide the label visually -->
<button>
<span class="assistiveText">Enter site</span>
</button>

[A11Y_DOM_04] Links must have non-empty text content

For a graphical link, use a ui:image instead. To include hidden link text, use a span tag with assistiveText class. For
buttons, use the ui:button component.
<!-- Method 1: Use an img tag with the alt attribute to provide link text -->
<a href="routes.html">
<img src="routes.png" alt="current routes" />
</a>

<!-- Method 2: Use a span tag with assistiveText class to provide link text -->
<a href="javascript:void(0);">
<span class="assistiveText">Toggle Notifications</span>
<div class="notificationCounter"></div>
</a>

[A11Y_DOM_05] Text color contrast ratio must meet the minimum requirement
Small text must have a contrast ratio of not less than 4.5:1. Small text includes those whose font size are:
• Smaller than 19px bold or semibold
• Smaller than 24px normal

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Creating Components Resolving Accessibility Errors

Large text must have a contrast ratio of not less than 3.0:1. Large text includes those whose font size are:
• At least 19px bold or semibold
• At least 24px normal
A good color contrast ratio means that the foreground and background color provides enough contrast when viewed by a user who
might have impaired vision or when viewed on a black and white screen. You can install Accessibility Developer Tools on your Google
Chrome browser or use the WebAim Color Contrast Checker tool.
[A11Y_DOM_06] Each frame and iframe element must have a non-empty title attribute
If using an iframe element, include a descriptive title attribute.
<iframe src="banner-ad.html" id="testiframe" name="testiframe" title="Advertisement">
<a href="banner-ad.html">Advertisement</a>
</iframe>

[A11Y_DOM_07] The head section must have a non-empty title element

In the head element, include a descriptive title tag.
<head>
<title>Welcome</title>
</head>

[A11Y_DOM_08] Data table cells must be associated with data table headers
Use the scope attribute or use both the id and header attributes.
<!-- Method 1: Use the scope attribute -->
<table border="1"><caption>Contact Information</caption>
<tr>
<th scope="col">Name</th>
<th scope="col">Department</th>
</tr>
<tr>
<td>admin</td>
<td>R&D</td>
</tr>
</table>

<!-- Method 2: Use the id and headers attributes -->

<table border="1">
<tr>
<th id="e1">First Name</th>
<th id="e2">Last Name</th>
<th id="e3">Department</th>
</tr>
<tr>
<td headers="e1">John</td>
<td headers="e2">Smith</td>
<td headers="e3">R&D</td>
</tr>
</table>

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Creating Components Resolving Accessibility Errors

[A11Y_DOM_09] Fieldset must have a legend element

Include a descriptive legend in your fieldset element.
<fieldset>
<legend>Choose yes or no</legend>
</fieldset>

[A11Y_DOM_10] Related radio buttons or checkboxes must be grouped with a fieldset

Nest your radio buttons and checkboxes in a fieldset tag.
<fieldset>
<legend>Choose yes or no</legend>
<input type="radio" name="yes" id="yesid" value="yes"/>
<label for="yesid">yes</label>
<input type="radio" name="no" id="noid" value="no"/>
<label for="noid">no</label>
</fieldset>

[A11Y_DOM_11] Headings should be properly nested

Headings should increase no more than one level each time, and can start at any level.
<h2>Profile</h2>
<h3>Profile Details</h3>
<h2>Interests</h2>

[A11Y_DOM_12] Base and top panels should have proper aria-hidden properties
The aria-hidden attribute indicates whether an element is hidden or not, and can be set to true or false respectively.
<!-- aria-hidden of base panel is false if top panel is not active -->
<section class="stage panelSlide forceAccess" aria-hidden="false"></div>
<div class="panel panelOverlay" aria-hidden="true"></div>

<!-- aria-hidden of base panel is true if there is active top panel -->
<section class="stage panelSlide forceAccess" aria-hidden="true"></div>
<div class="panel panelOverlay active" aria-hidden="false"></div>

[A11Y_DOM_13] Aria-describedby must be used to associate error message with input control
The aria-describedby attribute indicates the IDs of the elements that describe the object, and can be used to associate static
text with groups of elements. For more information, see Help and Error Messages on page 88.
<label for="fname">First name</label>
<input name="firstname" type="text" id="fname" aria-describedby="msgid">
<ul class="uiInputDefaultError" id="msgid">

[A11Y_DOM_14] Button must not have duplicate values

Text values in buttons should be unique.
<!-- Example 1 -->
<button>
<span class="assistiveText">My help text</span>
My other text
</button>

<!-- Example 2 -->

<button>
My text

94
Creating Components Add Components to Apps

<img src="icon.gif" alt="My other text">

</button>

[A11Y_DOM_15] A label was found without an associated input. Labels should only be used to identify inputs.
Each label should be associated to one input only. Check that you’re not accidentally creating two labels for an input. For example,
if you’re using ui:label to create a label for a ui:inputText component, don’t use the label and
labelDisplay="false" attributes on the component. You should only use labelDisplay="false" if your input
doesn’t have a visible label. For more information, see Forms, Fields, and Labels.

Add Components to Apps

When you’re ready to add components to your app, you should first look at the out-of-the-box components that come with the framework.
You can also leverage these components by extending them or using composition to add them to custom components that you’re
building.

Note: See the Components folder in the Reference tab for all the out-of-the-box components. The ui namespace includes
many components that are common on Web pages.
Components are encapsulated and their internals stay private, while their public shape is visible to consumers of the component. This
strong separation gives component authors freedom to change the internal implementation details and insulates component consumers
from those changes.
The public shape of a component is defined by the attributes that can be set and the events that interact with the component. The
shape is essentially the API for developers to interact with the component. To design a new component, think about the attributes that
you want to expose and the events that the component should initiate or respond to.
Once you have defined the shape of any new components, developers can work on the components in parallel. This is a useful approach
if you have a team working on an app.

SEE ALSO:
Component Composition
Using Object-Oriented Development
Component Attributes
Communicating with Events

95
CHAPTER 4 Communicating with Events
In this chapter ... The framework uses event-driven programming. You write handlers that respond to interface events as
they occur. The events may or may not have been triggered by user interaction.
• Actions and Events
In Aura, events are fired from JavaScript controller actions. Events can contain attributes that can be set
• Handling Events with
before the event is fired and read when the event is handled.
Client-Side
Controllers Events are declared by the aura:event tag in a .evt file, and they can have one of two types:
• Component Events component or application.
• Application Events Component Events
• Event Handling A component event is fired from an instance of a component. A component event can be handled
Lifecycle by the component that fired the event or by a component in the containment hierarchy that receives
the event.
• Advanced Events
Example Application Events
• Firing Aura Events Application events follow a traditional publish-subscribe model. An application event is fired from
from Non-Aura Code an instance of a component. All components that provide a handler for the event are notified.
• Events Best Practices Note: Always try to use a component event instead of an application event, if possible. Component
• Events Fired During events can only be handled by components above them in the containment hierarchy so their
the Rendering usage is more localized to the components that need to know about them. Application events
Lifecycle are best used for something that should be handled at the application level, such as navigating
• System Events to a specific record. Application events allow communication between components that are in
separate parts of the application and have no direct containment relationship.

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Communicating with Events Actions and Events

Actions and Events

The framework uses events to communicate data between components. Events are usually triggered by a user action.
Actions
User interaction with an element on a component or app. User actions trigger events, but events aren’t always explicitly triggered
by user actions. This type of action is not the same as a client-side JavaScript controller, which is sometimes known as a controller
action. The following button is wired up to a browser onclick event in response to a button click.
<lightning:button label = "Click Me" onclick = "{!c.handleClick}" />

Clicking the button invokes the handleClick method in the component’s client-side controller.
Events
A notification by the browser regarding an action. Browser events are handled by client-side JavaScript controllers, as shown in the
previous example. A browser event is not the same as a framework component event or application event, which you can create and
fire in a JavaScript controller to communicate data between components. For example, you can wire up the click event of a checkbox
to a client-side controller, which fires a component event to communicate relevant data to a parent component.
Another type of event, known as a system event, is fired automatically by the framework during its lifecycle, such as during component
initialization, change of an attribute value, and rendering. Components can handle a system event by registering the event in the
component markup.
The following diagram describes what happens when a user clicks a button that requires the component to retrieve data from the server.

1. User clicks a button or interacts with a component, triggering a browser event. For example, you want to save data from the server
when the button is clicked.
2. The button click invokes a client-side JavaScript controller, which provides some custom logic before invoking a helper function.
3. The JavaScript controller invokes a helper function. A helper function improves code reuse but it’s optional for this example.
4. The helper function calls a server-side controller method and queues the action.
5. The server-side method is invoked and data is returned.
6. A JavaScript callback function is invoked when the server-sideApex method completes.
7. The JavaScript callback function evaluates logic and updates the component’s UI.

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Communicating with Events Handling Events with Client-Side Controllers

8. User sees the updated component.

SEE ALSO:
Handling Events with Client-Side Controllers
Detecting Data Changes with Change Handlers
Calling a Server-Side Action
Events Fired During the Rendering Lifecycle

Handling Events with Client-Side Controllers

A client-side controller handles events within a component. It’s a JavaScript file that defines the functions for all of the component’s
actions.
A client-side controller is a JavaScript object in object-literal notation containing a map of name-value pairs. Each name corresponds to
a client-side action. Its value is the function code associated with the action. Client-side controllers are surrounded by parentheses and
curly braces. Separate action handlers with commas (as you would with any JavaScript map).
({
myAction : function(cmp, event, helper) {
// add code for the action
},

anotherAction : function(cmp, event, helper) {

// add code for the action
}
})

Each action function takes in three parameters:

1. cmp—The component to which the controller belongs.
2. event—The event that the action is handling.
3. helper—The component’s helper, which is optional. A helper contains functions that can be reused by any JavaScript code in
the component bundle.

Creating a Client-Side Controller

A client-side controller is part of the component bundle. It is auto-wired via the naming convention,
componentNameController.js.
To reuse a client-side controller from another component, use the controller system attribute in aura:component. For
example, this component uses the auto-wired client-side controller for c.sampleComponent in
c/sampleComponent/sampleComponentController.js.

<aura:component
controller="js://c.sampleComponent">
...
</aura:component>

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Communicating with Events Handling Events with Client-Side Controllers

Calling Client-Side Controller Actions

The following example component creates two buttons to contrast an HTML button with <lightning:button>, which is a
standard Aura component. Clicking on these buttons updates the text component attribute with the specified values.
target.get("v.label") refers to the label attribute value on the button.
Component source
<aura:component>
<aura:attribute name="text" type="String" default="Just a string. Waiting for change."/>

<input type="button" value="Flawed HTML Button"

onclick="alert('this will not work')"/>
<br/>
<lightning:button label="Framework Button" onclick="{!c.handleClick}"/>
<br/>
{!v.text}
</aura:component>

If you know some JavaScript, you might be tempted to write something like the first "Flawed" button because you know that HTML tags
are first-class citizens in the framework. However, the "Flawed" button won't work because arbitrary JavaScript, such as the alert()
call, in the component is ignored.
The framework has its own event system. DOM events are mapped to Aura events, since HTML tags are mapped to Aura components.
Any browser DOM element event starting with on, such as onclick or onkeypress, can be wired to a controller action. You can
only wire browser events to controller actions.
The "Framework" button wires the onclick attribute in the <lightning:button> component to the handleClick action
in the controller.
Client-side controller source
({
handleClick : function(cmp, event) {
var attributeValue = cmp.get("v.text");
console.log("current text: " + attributeValue);

var target = event.getSource();

cmp.set("v.text", target.get("v.label"));
}
})

The handleClick action uses event.getSource() to get the source component that fired this component event. In this
case, the source component is the <lightning:button> in the markup.
The code then sets the value of the text component attribute to the value of the button’s label attribute. The text component
attribute is defined in the <aura:attribute> tag in the markup.

Tip: Use unique names for client-side and server-side actions in a component. A JavaScript function (client-side action) with the
same name as a Java method (server-side action ) can lead to hard-to-debug issues. In PRODDEBUG mode, the framework logs a
browser console warning about the clashing client-side and server-side action names.

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Communicating with Events Component Events

Handling Framework Events

Handle framework events using actions in client-side component controllers. Framework events for common mouse and keyboard
interactions are available with out-of-the-box components. For example, if you use the lightning:input component, you have
access to its events, such as onfocus and onblur.

Accessing Component Attributes

In the handleClick function, notice that the first argument to every action is the component to which the controller belongs. One
of the most common things you'll want to do with this component is look at and change its attribute values.
cmp.get("v.attributeName") returns the value of the attributeName attribute.
cmp.set("v.attributeName", "attribute value") sets the value of the attributeName attribute.

Invoking Another Action in the Controller

To call an action method from another method, put the common code in a helper function and invoke it using
helper.someFunction(cmp).

SEE ALSO:
Sharing JavaScript Code in a Component Bundle
Event Handling Lifecycle
Creating Server-Side Logic with Controllers

Component Events
A component event is fired from an instance of a component. A component event can be handled by the component that fired the
event or by a component in the containment hierarchy that receives the event.

Note: To communicate from a parent component to a child component that it contains, use <aura:method> to call a method
in the child component’s client-side controller from the parent component. Using <aura:method> is easier than getting an
instance of the child component in the parent component, and then firing and handling a component event.
When a component contains another component, we refer in the documentation to parent and child components in the containment
hierarchy. When a component extends another component, we refer to sub and super components in the inheritance hierarchy.

IN THIS SECTION:
Component Event Propagation
The framework supports capture and bubble phases for the propagation of component events. These phases are similar to DOM
handling patterns and provide an opportunity for interested components to interact with an event and potentially control the
behavior for subsequent handlers.
Create Custom Component Events
Create a custom component event using the <aura:event> tag in a .evt resource. Events can contain attributes that can
be set before the event is fired and read when the event is handled.

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Communicating with Events Component Event Propagation

Fire Component Events

Fire a component event to communicate data to another component. A component event can be handled by the component that
fired the event or by a component in the containment hierarchy that receives the event.
Handling Component Events
A component event can be handled by the component that fired the event or by a component in the containment hierarchy that
receives the event.

SEE ALSO:
aura:method
Application Events
Handling Events with Client-Side Controllers
Advanced Events Example
What is Inherited?

Component Event Propagation

The framework supports capture and bubble phases for the propagation of component events. These phases are similar to DOM handling
patterns and provide an opportunity for interested components to interact with an event and potentially control the behavior for
subsequent handlers.
The component that fires an event is known as the source component. The framework allows you to handle the event in different phases.
These phases give you flexibility for how to best process the event for your application.
The phases are:
Capture
The event is captured and trickles down from the application root to the source component. The event can be handled by a component
in the containment hierarchy that receives the captured event.
Event handlers are invoked in order from the application root down to the source component that fired the event.
Any registered handler in this phase can stop the event from propagating, at which point no more handlers are called in this phase
or the bubble phase.
Bubble
The component that fired the event can handle it. The event then bubbles up from the source component to the application root.
The event can be handled by a component in the containment hierarchy that receives the bubbled event.
Event handlers are invoked in order from the source component that fired the event up to the application root.
Any registered handler in this phase can stop the event from propagating, at which point no more handlers are called in this phase.
Here’s the sequence of component event propagation.
1. Event fired—A component event is fired.
2. Capture phase—The framework executes the capture phase from the application root to the source component until all components
are traversed. Any handling event can stop propagation by calling stopPropagation() on the event.
3. Bubble phase—The framework executes the bubble phase from the source component to the application root until all components
are traversed or stopPropagation() is called.

Note: Application events have a separate default phase. There’s no separate default phase for component events. The default
phase is the bubble phase.

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Communicating with Events Create Custom Component Events

Create Custom Component Events

Create a custom component event using the <aura:event> tag in a .evt resource. Events can contain attributes that can be set
before the event is fired and read when the event is handled.
Use type="COMPONENT" in the <aura:event> tag for a component event. For example, this c:compEvent component
event has one attribute with a name of message.
<!--c:compEvent-->
<aura:event type="COMPONENT">
<!-- Add aura:attribute tags to define event shape.
One sample attribute here. -->
<aura:attribute name="message" type="String"/>
</aura:event>

The component that fires an event can set the event’s data. To set the attribute values, call event.setParam() or
event.setParams(). A parameter name set in the event must match the name attribute of an <aura:attribute> in the
event. For example, if you fire c:compEvent, you could use:
event.setParam("message", "event message here");

The component that handles an event can retrieve the event data. To retrieve the attribute value in this event, call
event.getParam("message") in the handler’s client-side controller.

Fire Component Events

Fire a component event to communicate data to another component. A component event can be handled by the component that fired
the event or by a component in the containment hierarchy that receives the event.

Register an Event
A component registers that it may fire an event by using <aura:registerEvent> in its markup. For example:
<aura:registerEvent name="sampleComponentEvent" type="c:compEvent"/>

We’ll see how the value of the name attribute is used for firing and handling events.

Fire an Event
To get a reference to a component event in JavaScript, use cmp.getEvent("evtName") where evtName matches the name
attribute in <aura:registerEvent>.
Use fire() to fire the event from an instance of a component. For example, in an action function in a client-side controller:
var compEvent = cmp.getEvent("sampleComponentEvent");
// Optional: set some data for the event (also known as event shape)
// A parameter’s name must match the name attribute
// of one of the event’s <aura:attribute> tags
// compEvent.setParams({"myParam" : myValue });
compEvent.fire();

SEE ALSO:
Fire Application Events

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Communicating with Events Handling Component Events

Handling Component Events

A component event can be handled by the component that fired the event or by a component in the containment hierarchy that receives
the event.
Use <aura:handler> in the markup of the handler component. For example:
<aura:handler name="sampleComponentEvent" event="c:compEvent"
action="{!c.handleComponentEvent}"/>

The name attribute in <aura:handler> must match the name attribute in the <aura:registerEvent> tag in the
component that fires the event.
The action attribute of <aura:handler> sets the client-side controller action to handle the event.
The event attribute specifies the event being handled. The format is namespace:eventName.
In this example, when the event is fired, the handleComponentEvent client-side controller action is called.

Event Handling Phases

Component event handlers are associated with the bubble phase by default. To add a handler for the capture phase instead, use the
phase attribute.

<aura:handler name="sampleComponentEvent" event="ns:eventName"

action="{!c.handleComponentEvent}" phase="capture" />

Get the Source of an Event

In the client-side controller action for an <aura:handler> tag, use evt.getSource() to find out which component fired the
event, where evt is a reference to the event. To retrieve the source element, use evt.getSource().getElement().

IN THIS SECTION:
Component Handling Its Own Event
A component can handle its own event by using the <aura:handler> tag in its markup.
Handle Component Event of Instantiated Component
A parent component can set a handler action when it instantiates a child component in its markup.
Handling Bubbled or Captured Component Events
Event propagation rules determine which components in the containment hierarchy can handle events by default in the bubble or
capture phases. Learn about the rules and how to handle events in the bubble or capture phases.
Handling Component Events Dynamically
A component can have its handler bound dynamically via JavaScript. This is useful if a component is created in JavaScript on the
client-side.

SEE ALSO:
Component Event Propagation
Handling Application Events

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Communicating with Events Handling Component Events

Component Handling Its Own Event

A component can handle its own event by using the <aura:handler> tag in its markup.
The action attribute of <aura:handler> sets the client-side controller action to handle the event. For example:
<aura:registerEvent name="sampleComponentEvent" type="c:compEvent"/>
<aura:handler name="sampleComponentEvent" event="c:compEvent"
action="{!c.handleSampleEvent}"/>

Note: The name attributes in <aura:registerEvent> and <aura:handler> must match, since each event is
defined by its name.

SEE ALSO:
Handle Component Event of Instantiated Component

Handle Component Event of Instantiated Component

A parent component can set a handler action when it instantiates a child component in its markup.
Let’s a look at an example. c:child registers that it may fire a sampleComponentEvent event by using
<aura:registerEvent> in its markup.

<!-- c:child -->

<aura:component>
<aura:registerEvent name="sampleComponentEvent" type="c:compEvent"/>
</aura:component>

c:parent sets a handler for this event when it instantiates c:child in its markup.

<!-- parent.cmp -->

<aura:component>
<c:child sampleComponentEvent="{!c.handleChildEvent}"/>
</aura:component>

Note how c:parent uses the following syntax to set a handler for the sampleComponentEvent event fired by c:child.
<c:child sampleComponentEvent="{!c.handleChildEvent}"/>

The syntax looks similar to how you set an attribute called sampleComponentEvent. However, in this case,
sampleComponentEvent isn’t an attribute. sampleComponentEvent matches the event name declared in c:child.

<aura:registerEvent name="sampleComponentEvent" type="c:compEvent"/>

The preceding syntax is a convenient shortcut for the normal way that a component declares a handler for an event. The parent component
can only use this syntax to handle events from a direct descendent. If you want to be more explicit in c:parent that you’re handling
an event, or if the event might be fired by a component further down the component hierarchy, use an <aura:handler> tag
instead of declaring the handler within the <c:child> tag.
<!-- parent.cmp -->
<aura:component>
<aura:handler name="sampleComponentEvent" event="c:compEvent"
action="{!c.handleSampleEvent}"/>
<c:child />
</aura:component>

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The two versions of c:parent markup behave the same. However, using <aura:handler> makes it more obvious that you’re
handling a sampleComponentEvent event.

SEE ALSO:
Component Handling Its Own Event
Handling Bubbled or Captured Component Events

Handling Bubbled or Captured Component Events

Event propagation rules determine which components in the containment hierarchy can handle events by default in the bubble or
capture phases. Learn about the rules and how to handle events in the bubble or capture phases.
The framework supports capture and bubble phases for the propagation of component events. These phases are similar to DOM handling
patterns and provide an opportunity for interested components to interact with an event and potentially control the behavior for
subsequent handlers. The capture phase executes before the bubble phase.

Default Event Propagation Rules

By default, every parent in the containment hierarchy can’t handle an event during the capture and bubble phases. Instead, the event
propagates to every owner in the containment hierarchy.
A component’s owner is the component that is responsible for its creation. For declaratively created components, the owner is the
outermost component containing the markup that references the component firing the event. For programmatically created components,
the owner component is the component that invoked $A.createComponent to create it.
The same rules apply for the capture phase, although the direction of event propagation (down) is the opposite of the bubble phase
(up).
Confused? It makes more sense when you look at an example in the bubbling phase.
c:owner contains c:container, which in turn contains c:eventSource.

<!--c:owner-->
<aura:component>
<c:container>
<c:eventSource />
</c:container>
</aura:component>

If c:eventSource fires an event, it can handle the event itself. The event then bubbles up the containment hierarchy.
c:container contains c:eventSource but it’s not the owner because it’s not the outermost component in the markup, so it
can’t handle the bubbled event.
c:owner is the owner because c:container is in its markup. c:owner can handle the event.

Propagation to All Container Components

The default behavior doesn’t allow an event to be handled by every parent in the containment hierarchy. Some components contain
other components but aren’t the owner of those components. These components are known as container components. In the example,
c:container is a container component because it’s not the owner for c:eventSource. By default, c:container can’t
handle events fired by c:eventSource.

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A container component has a facet attribute whose type is Aura.Component[], such as the default body attribute. The container
component includes those components in its definition using an expression, such as {!v.body}. The container component isn’t the
owner of the components rendered with that expression.
To allow a container component to handle the event, add includeFacets="true" to the <aura:handler> tag of the
container component. For example, adding includeFacets="true" to the handler in the container component, c:container,
enables it to handle the component event bubbled from c:eventSource.
<aura:handler name="bubblingEvent" event="c:compEvent" action="{!c.handleBubbling}"
includeFacets="true" />

Handle Bubbled Event

A component that fires a component event registers that it fires the event by using the <aura:registerEvent> tag.
<aura:component>
<aura:registerEvent name="compEvent" type="c:compEvent" />
</aura:component>

A component handling the event in the bubble phase uses the <aura:handler> tag to assign a handling action in its client-side
controller.
<aura:component>
<aura:handler name="compEvent" event="c:compEvent" action="{!c.handleBubbling}"/>
</aura:component>

Note: The name attribute in <aura:handler> must match the name attribute in the <aura:registerEvent> tag
in the component that fires the event.

Handle Captured Event

A component handling the event in the capture phase uses the <aura:handler> tag to assign a handling action in its client-side
controller.
<aura:component>
<aura:handler name="compEvent" event="c:compEvent" action="{!c.handleCapture}"
phase="capture" />
</aura:component>

The default handling phase for component events is bubble if no phase attribute is set.

Stop Event Propagation

Use the stopPropagation() method in the Event object to stop the event propagating to other components.

Pausing Event Propagation for Asynchronous Code Execution

Use event.pause() to pause event handling and propagation until event.resume() is called. This flow-control mechanism
is useful for any decision that depends on the response from the execution of asynchronous code. For example, you might make a
decision about event propagation based on the response from an asynchronous call to native mobile code.
You can call pause() or resume() in the capture or bubble phases.

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Event Bubbling Example

Let’s look at an example so you can play around with it yourself.
<!--c:eventBubblingParent-->
<aura:component>
<c:eventBubblingChild>
<c:eventBubblingGrandchild />
</c:eventBubblingChild>
</aura:component>

First, we define a simple component event.

<!--c:compEvent-->
<aura:event type="COMPONENT">
<!--simple event with no attributes-->
</aura:event>

c:eventBubblingEmitter is the component that fires c:compEvent.

<!--c:eventBubblingEmitter-->
<aura:component>
<aura:registerEvent name="bubblingEvent" type="c:compEvent" />
<lightning:button onclick="{!c.fireEvent}" label="Start Bubbling"/>
</aura:component>

Here’s the controller for c:eventBubblingEmitter. When you press the button, it fires the bubblingEvent event registered
in the markup.
/*eventBubblingEmitterController.js*/
{
fireEvent : function(cmp) {
var cmpEvent = cmp.getEvent("bubblingEvent");
cmpEvent.fire();
}
}

c:eventBubblingGrandchild contains c:eventBubblingEmitter and uses <aura:handler> to assign a handler

for the event.
<!--c:eventBubblingGrandchild-->
<aura:component>
<aura:handler name="bubblingEvent" event="c:compEvent" action="{!c.handleBubbling}"/>

<div class="grandchild">
<c:eventBubblingEmitter />
</div>
</aura:component>

Here’s the controller for c:eventBubblingGrandchild.

/*eventBubblingGrandchildController.js*/
{
handleBubbling : function(component, event) {
console.log("Grandchild handler for " + event.getName());

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}
}

The controller logs the event name when the handler is called.
Here’s the markup for c:eventBubblingChild. We will pass c:eventBubblingGrandchild in as the body of
c:eventBubblingChild when we create c:eventBubblingParent later in this example.

<!--c:eventBubblingChild-->
<aura:component>
<aura:handler name="bubblingEvent" event="c:compEvent" action="{!c.handleBubbling}"/>

<div class="child">
{!v.body}
</div>
</aura:component>

Here’s the controller for c:eventBubblingChild.

/*eventBubblingChildController.js*/
{
handleBubbling : function(component, event) {
console.log("Child handler for " + event.getName());
}
}

c:eventBubblingParent contains c:eventBubblingChild, which in turn contains c:eventBubblingGrandchild.

<!--c:eventBubblingParent-->
<aura:component>
<aura:handler name="bubblingEvent" event="c:compEvent" action="{!c.handleBubbling}"/>

<div class="parent">
<c:eventBubblingChild>
<c:eventBubblingGrandchild />
</c:eventBubblingChild>
</div>
</aura:component>

Here’s the controller for c:eventBubblingParent.

/*eventBubblingParentController.js*/
{
handleBubbling : function(component, event) {
console.log("Parent handler for " + event.getName());
}
}

Now, let’s see what happens when you run the code.
1. In your browser, navigate to c:eventBubblingParent.
2. Click the Start Bubbling button that is part of the markup in c:eventBubblingEmitter.

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3. Note the output in your browser’s console:

Grandchild handler for bubblingEvent
Parent handler for bubblingEvent

The c:compEvent event is bubbled to c:eventBubblingGrandchild and c:eventBubblingParent as they are

owners in the containment hierarchy. The event is not handled by c:eventBubblingChild as c:eventBubblingChild
is in the markup for c:eventBubblingParent but it’s not an owner as it’s not the outermost component in that markup.
Now, let’s see how to stop event propagation. Edit the controller for c:eventBubblingGrandchild to stop propagation.
/*eventBubblingGrandchildController.js*/
{
handleBubbling : function(component, event) {
console.log("Grandchild handler for " + event.getName());
event.stopPropagation();
}
}

Now, navigate to c:eventBubblingParent and click the Start Bubbling button.

Note the output in your browser’s console:
Grandchild handler for bubblingEvent

The event no longer bubbles up to the c:eventBubblingParent component.

SEE ALSO:
Component Event Propagation
Handle Component Event of Instantiated Component

Handling Component Events Dynamically

A component can have its handler bound dynamically via JavaScript. This is useful if a component is created in JavaScript on the client-side.
For more information, see Dynamically Adding Event Handlers To a Component on page 187.

Component Event Example

Here’s a simple use case of using a component event to update an attribute in another component.
1. A user clicks a button in the notifier component, ceNotifier.cmp.
2. The client-side controller for ceNotifier.cmp sets a message in a component event and fires the event.
3. The handler component, ceHandler.cmp, contains the notifier component, and handles the fired event.
4. The client-side controller for ceHandler.cmp sets an attribute in ceHandler.cmp based on the data sent in the event.

Component Event
The ceEvent.evt component event has one attribute. We’ll use this attribute to pass some data in the event when it’s fired.
<!--c:ceEvent-->
<aura:event type="COMPONENT">

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<aura:attribute name="message" type="String"/>

</aura:event>

Notifier Component
The c:ceNotifier component uses aura:registerEvent to declare that it may fire the component event.
The button in the component contains an onclick browser event that is wired to the fireComponentEvent action in the
client-side controller. The action is invoked when you click the button.
<!--c:ceNotifier-->
<aura:component>
<aura:registerEvent name="cmpEvent" type="c:ceEvent"/>

<h1>Simple Component Event Sample</h1>

<p><lightning:button
label="Click here to fire a component event"
onclick="{!c.fireComponentEvent}" />
</p>
</aura:component>

The client-side controller gets an instance of the event by calling cmp.getEvent("cmpEvent"), where cmpEvent matches
the value of the name attribute in the <aura:registerEvent> tag in the component markup. The controller sets the message
attribute of the event and fires the event.
/* ceNotifierController.js */
{
fireComponentEvent : function(cmp, event) {
// Get the component event by using the
// name value from aura:registerEvent
var cmpEvent = cmp.getEvent("cmpEvent");
cmpEvent.setParams({
"message" : "A component event fired me. " +
"It all happened so fast. Now, I'm here!" });
cmpEvent.fire();
}
}

Handler Component
The c:ceHandler handler component contains the c:ceNotifier component. The <aura:handler> tag uses the same
value of the name attribute, cmpEvent, from the <aura:registerEvent> tag in c:ceNotifier. This wires up
c:ceHandler to handle the event bubbled up from c:ceNotifier.
When the event is fired, the handleComponentEvent action in the client-side controller of the handler component is invoked.
<!--c:ceHandler-->
<aura:component>
<aura:attribute name="messageFromEvent" type="String"/>
<aura:attribute name="numEvents" type="Integer" default="0"/>

<!-- Note that name="cmpEvent" in aura:registerEvent

in ceNotifier.cmp -->
<aura:handler name="cmpEvent" event="c:ceEvent" action="{!c.handleComponentEvent}"/>

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<!-- handler contains the notifier component -->

<c:ceNotifier />

<p>{!v.messageFromEvent}</p>
<p>Number of events: {!v.numEvents}</p>

</aura:component>

The controller retrieves the data sent in the event and uses it to update the messageFromEvent attribute in the handler component.
/* ceHandlerController.js */
{
handleComponentEvent : function(cmp, event) {
var message = event.getParam("message");

// set the handler attributes based on event data

cmp.set("v.messageFromEvent", message);
var numEventsHandled = parseInt(cmp.get("v.numEvents")) + 1;
cmp.set("v.numEvents", numEventsHandled);
}
}

Put It All Together

Navigate to the c:ceHandler component and click the button to fire the component event.
http://localhost:<port>/c/ceHandler.cmp.
If you want to access data on the server, you could extend this example to call a server-side controller from the handler’s client-side
controller.

SEE ALSO:
Component Events
Creating Server-Side Logic with Controllers
Application Event Example

Application Events
Application events follow a traditional publish-subscribe model. An application event is fired from an instance of a component. All
components that provide a handler for the event are notified.

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IN THIS SECTION:
Application Event Propagation
The framework supports capture, bubble, and default phases for the propagation of application events. The capture and bubble
phases are similar to DOM handling patterns and provide an opportunity for interested components to interact with an event and
potentially control the behavior for subsequent handlers. The default phase preserves the framework’s original handling behavior.
Create Custom Application Events
Create a custom application event using the <aura:event> tag in a .evt resource. Events can contain attributes that can be
set before the event is fired and read when the event is handled.
Fire Application Events
Application events follow a traditional publish-subscribe model. An application event is fired from an instance of a component. All
components that provide a handler for the event are notified.
Handling Application Events
Use <aura:handler> in the markup of the handler component.

SEE ALSO:
Component Events
Handling Events with Client-Side Controllers
Application Event Propagation
Advanced Events Example

Application Event Propagation

The framework supports capture, bubble, and default phases for the propagation of application events. The capture and bubble phases
are similar to DOM handling patterns and provide an opportunity for interested components to interact with an event and potentially
control the behavior for subsequent handlers. The default phase preserves the framework’s original handling behavior.
The component that fires an event is known as the source component. The framework allows you to handle the event in different phases.
These phases give you flexibility for how to best process the event for your application.
The phases are:

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Communicating with Events Create Custom Application Events

Capture
The event is captured and trickles down from the application root to the source component. The event can be handled by a component
in the containment hierarchy that receives the captured event.
Event handlers are invoked in order from the application root down to the source component that fired the event.
Any registered handler in this phase can stop the event from propagating, at which point no more handlers are called in this phase
or the bubble phase. If a component stops the event propagation using event.stopPropagation(), the component
becomes the root node used in the default phase.
Any registered handler in this phase can cancel the default behavior of the event by calling event.preventDefault(). This
call prevents execution of any of the handlers in the default phase.
Bubble
The component that fired the event can handle it. The event then bubbles up from the source component to the application root.
The event can be handled by a component in the containment hierarchy that receives the bubbled event.
Event handlers are invoked in order from the source component that fired the event up to the application root.
Any registered handler in this phase can stop the event from propagating, at which point no more handlers will be called in this
phase. If a component stops the event propagation using event.stopPropagation(), the component becomes the root
node used in the default phase.
Any registered handler in this phase can cancel the default behavior of the event by calling event.preventDefault(). This
call prevents execution of any of the handlers in the default phase.
Default
Event handlers are invoked in a non-deterministic order from the root node through its subtree. The default phase doesn’t have the
same propagation rules related to component hierarchy as the capture and bubble phases. The default phase can be useful for
handling application events that affect components in different sub-trees of your app.
If the event’s propagation wasn’t stopped in a previous phase, the root node defaults to the application root. If the event’s propagation
was stopped in a previous phase, the root node is set to the component whose handler invoked event.stopPropagation().
Here is the sequence of application event propagation.
1. Event fired—An application event is fired. The component that fires the event is known as the source component.
2. Capture phase—The framework executes the capture phase from the application root to the source component until all components
are traversed. Any handling event can stop propagation by calling stopPropagation() on the event.
3. Bubble phase—The framework executes the bubble phase from the source component to the application root until all components
are traversed or stopPropagation() is called.
4. Default phase—The framework executes the default phase from the root node unless preventDefault() was called in the
capture or bubble phases. If the event’s propagation wasn’t stopped in a previous phase, the root node defaults to the application
root. If the event’s propagation was stopped in a previous phase, the root node is set to the component whose handler invoked
event.stopPropagation().

Create Custom Application Events

Create a custom application event using the <aura:event> tag in a .evt resource. Events can contain attributes that can be set
before the event is fired and read when the event is handled.
Use type="APPLICATION" in the <aura:event> tag for an application event. For example, this c:appEvent application
event has one attribute with a name of message.
<!--c:appEvent-->
<aura:event type="APPLICATION">

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<!-- Add aura:attribute tags to define event shape.

One sample attribute here. -->
<aura:attribute name="message" type="String"/>
</aura:event>

The component that fires an event can set the event’s data. To set the attribute values, call event.setParam() or
event.setParams(). A parameter name set in the event must match the name attribute of an <aura:attribute> in the
event. For example, if you fire c:appEvent, you could use:
event.setParam("message", "event message here");

The component that handles an event can retrieve the event data. To retrieve the attribute in this event, call
event.getParam("message") in the handler’s client-side controller.

Fire Application Events

Application events follow a traditional publish-subscribe model. An application event is fired from an instance of a component. All
components that provide a handler for the event are notified.

Register an Event
A component registers that it may fire an application event by using <aura:registerEvent> in its markup. The name attribute
is required but not used for application events. The name attribute is only relevant for component events. This example uses
name="appEvent" but the value isn’t used anywhere.

<aura:registerEvent name="appEvent" type="c:appEvent"/>

Fire an Event
Use $A.get("e.myNamespace:myAppEvent") in JavaScript to get an instance of the myAppEvent event in the
myNamespace namespace.

Note: The syntax to get an instance of an application event is different than the syntax to get a component event, which is
cmp.getEvent("evtName").
Use fire() to fire the event.
var appEvent = $A.get("e.c:appEvent");
// Optional: set some data for the event (also known as event shape)
// A parameter’s name must match the name attribute
// of one of the event’s <aura:attribute> tags
//appEvent.setParams({ "myParam" : myValue });
appEvent.fire();

Events Fired on App Rendering

Several events are fired when an app is rendering. All init events are fired to indicate the component or app has been initialized. If a
component is contained in another component or app, the inner component is initialized first.
If a server call is made during rendering, aura:waiting is fired. When the framework receives a server response,
aura:doneWaiting is fired.
Finally, aura:doneRendering is fired when all rendering has been completed.

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Note: We don't recommend using the legacy aura:waiting, aura:doneWaiting, and aura:doneRendering
application events except as a last resort. The aura:waiting and aura:doneWaiting application events are fired for
every batched server request, even for requests from other components in your app. Unless your component is running in complete
isolation in a standalone app and not included in Lightning Experience or the Salesforce app, you probably don’t want to handle
these application events. The container app may fire server-side actions and trigger your event handlers multiple times.
For more information, see Events Fired During the Rendering Lifecycle on page 127.

SEE ALSO:
Fire Component Events

Handling Application Events

Use <aura:handler> in the markup of the handler component.
For example:
<aura:handler event="c:appEvent" action="{!c.handleApplicationEvent}"/>

The event attribute specifies the event being handled. The format is namespace:eventName.
The action attribute of <aura:handler> sets the client-side controller action to handle the event.

Note: The handler for an application event won’t work if you set the name attribute in <aura:handler>. Use the name
attribute only when you’re handling component events.
In this example, when the event is fired, the handleApplicationEvent client-side controller action is called.

Event Handling Phases

The framework allows you to handle the event in different phases. These phases give you flexibility for how to best process the event
for your application.
Application event handlers are associated with the default phase. To add a handler for the capture or bubble phases instead, use the
phase attribute.

Get the Source of an Event

In the client-side controller action for an <aura:handler> tag, use evt.getSource() to find out which component fired the
event, where evt is a reference to the event. To retrieve the source element, use evt.getSource().getElement().

IN THIS SECTION:
Handling Bubbled or Captured Application Events
Event propagation rules determine which components in the containment hierarchy can handle events by default in the bubble or
capture phases. Learn about the rules and how to handle events in the bubble or capture phases.

SEE ALSO:
Handling Component Events

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Communicating with Events Handling Application Events

Handling Bubbled or Captured Application Events

Event propagation rules determine which components in the containment hierarchy can handle events by default in the bubble or
capture phases. Learn about the rules and how to handle events in the bubble or capture phases.
The framework supports capture, bubble, and default phases for the propagation of application events. The capture and bubble phases
are similar to DOM handling patterns and provide an opportunity for interested components to interact with an event and potentially
control the behavior for subsequent handlers. The default phase preserves the framework’s original handling behavior.

Default Event Propagation Rules

By default, every parent in the containment hierarchy can’t handle an event during the capture and bubble phases. Instead, the event
propagates to every owner in the containment hierarchy.
A component’s owner is the component that is responsible for its creation. For declaratively created components, the owner is the
outermost component containing the markup that references the component firing the event. For programmatically created components,
the owner component is the component that invoked $A.createComponent to create it.
The same rules apply for the capture phase, although the direction of event propagation (down) is the opposite of the bubble phase
(up).
Confused? It makes more sense when you look at an example in the bubbling phase.
c:owner contains c:container, which in turn contains c:eventSource.

<!--c:owner-->
<aura:component>
<c:container>
<c:eventSource />
</c:container>
</aura:component>

If c:eventSource fires an event, it can handle the event itself. The event then bubbles up the containment hierarchy.
c:container contains c:eventSource but it’s not the owner because it’s not the outermost component in the markup, so it
can’t handle the bubbled event.
c:owner is the owner because c:container is in its markup. c:owner can handle the event.

Propagation to All Container Components

The default behavior doesn’t allow an event to be handled by every parent in the containment hierarchy. Some components contain
other components but aren’t the owner of those components. These components are known as container components. In the example,
c:container is a container component because it’s not the owner for c:eventSource. By default, c:container can’t
handle events fired by c:eventSource.
A container component has a facet attribute whose type is Aura.Component[], such as the default body attribute. The container
component includes those components in its definition using an expression, such as {!v.body}. The container component isn’t the
owner of the components rendered with that expression.
To allow a container component to handle the event, add includeFacets="true" to the <aura:handler> tag of the
container component. For example, adding includeFacets="true" to the handler in the container component, c:container,
enables it to handle the component event bubbled from c:eventSource.
<aura:handler name="bubblingEvent" event="c:compEvent" action="{!c.handleBubbling}"
includeFacets="true" />

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Handle Bubbled Event

To add a handler for the bubble phase, set phase="bubble".
<aura:handler event="c:appEvent" action="{!c.handleBubbledEvent}"
phase="bubble" />

The event attribute specifies the event being handled. The format is namespace:eventName.
The action attribute of <aura:handler> sets the client-side controller action to handle the event.

Handle Captured Event

To add a handler for the capture phase, set phase="capture".
<aura:handler event="c:appEvent" action="{!c.handleCapturedEvent}"
phase="capture" />

Stop Event Propagation

Use the stopPropagation() method in the Event object to stop the event propagating to other components.

Pausing Event Propagation for Asynchronous Code Execution

Use event.pause() to pause event handling and propagation until event.resume() is called. This flow-control mechanism
is useful for any decision that depends on the response from the execution of asynchronous code. For example, you might make a
decision about event propagation based on the response from an asynchronous call to native mobile code.
You can call pause() or resume() in the capture or bubble phases.

Application Event Example

Here’s a simple use case of using an application event to update an attribute in another component.
1. A user clicks a button in the notifier component, aeNotifier.cmp.
2. The client-side controller for aeNotifier.cmp sets a message in a component event and fires the event.
3. The handler component, aeHandler.cmp, handles the fired event.
4. The client-side controller for aeHandler.cmp sets an attribute in aeHandler.cmp based on the data sent in the event.

Application Event
The aeEvent.evt application event has one attribute. We’ll use this attribute to pass some data in the event when it’s fired.
<!--c:aeEvent-->
<aura:event type="APPLICATION">
<aura:attribute name="message" type="String"/>
</aura:event>

Notifier Component
The aeNotifier.cmp notifier component uses aura:registerEvent to declare that it may fire the application event. The
name attribute is required but not used for application events. The name attribute is only relevant for component events.

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The button in the component contains a onclick browser event that is wired to the fireApplicationEvent action in the
client-side controller. Clicking this button invokes the action.
<!--c:aeNotifier-->
<aura:component>
<aura:registerEvent name="appEvent" type="c:aeEvent"/>

<h1>Simple Application Event Sample</h1>

<p><lightning:button
label="Click here to fire an application event"
onclick="{!c.fireApplicationEvent}" />
</p>
</aura:component>

The client-side controller gets an instance of the event by calling $A.get("e.c:aeEvent"). The controller sets the message
attribute of the event and fires the event.
/* aeNotifierController.js */
{
fireApplicationEvent : function(cmp, event) {
// Get the application event by using the
// e.<namespace>.<event> syntax
var appEvent = $A.get("e.c:aeEvent");
appEvent.setParams({
"message" : "An application event fired me. " +
"It all happened so fast. Now, I'm everywhere!" });
appEvent.fire();
}
}

Handler Component
The aeHandler.cmp handler component uses the <aura:handler> tag to register that it handles the application event.

Note: The handler for an application event won’t work if you set the name attribute in <aura:handler>. Use the name
attribute only when you’re handling component events.
When the event is fired, the handleApplicationEvent action in the client-side controller of the handler component is invoked.
<!--c:aeHandler-->
<aura:component>
<aura:attribute name="messageFromEvent" type="String"/>
<aura:attribute name="numEvents" type="Integer" default="0"/>

<aura:handler event="c:aeEvent" action="{!c.handleApplicationEvent}"/>

<p>{!v.messageFromEvent}</p>
<p>Number of events: {!v.numEvents}</p>
</aura:component>

The controller retrieves the data sent in the event and uses it to update the messageFromEvent attribute in the handler component.
/* aeHandlerController.js */
{
handleApplicationEvent : function(cmp, event) {
var message = event.getParam("message");

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// set the handler attributes based on event data

cmp.set("v.messageFromEvent", message);
var numEventsHandled = parseInt(cmp.get("v.numEvents")) + 1;
cmp.set("v.numEvents", numEventsHandled);
}
}

Container Component
The aeContainer.cmp container component contains the notifier and handler components. This is different from the component
event example where the handler contains the notifier component.
<!--c:aeContainer-->
<aura:component>
<c:aeNotifier/>
<c:aeHandler/>
</aura:component>

Put It All Together

You can test this code by navigating to:
http://localhost:<port>/c/aeContainer.cmp.
If you want to access data on the server, you could extend this example to call a server-side controller from the handler’s client-side
controller.

SEE ALSO:
Application Events
Creating Server-Side Logic with Controllers
Component Event Example

Event Handling Lifecycle

The following chart summarizes how the framework handles events.

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Communicating with Events Event Handling Lifecycle

1 Detect Firing of Event

The framework detects the firing of an event. For example, the event could be triggered by a button click in a notifier component.
2 Determine the Event Type
2.1 Component Event
The parent or container component instance that fired the event is identified. This container component locates all relevant event
handlers for further processing.
2.2 Application Event
Any component can have an event handler for this event. All relevant event handlers are located.
3 Execute each Handler
3.1 Executing a Component Event Handler
Each of the event handlers defined in the container component for the event are executed by the handler controller, which can also:

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• Set attributes or modify data on the component (causing a re-rendering of the component).
• Fire another event or invoke a client-side or server-side action.
3.2 Executing an Application Event Handler
All event handlers are executed. When the event handler is executed, the event instance is passed into the event handler.
4 Re-render Component (optional)
After the event handlers and any callback actions are executed, a component might be automatically re-rendered if it was modified
during the event handling process.

SEE ALSO:
Create a Custom Renderer

Advanced Events Example

This example builds on the simpler component and application event examples. It uses one notifier component and one handler
component that work with both component and application events. Before we see a component wired up to events, let's look at the
individual resources involved.
This table summarizes the roles of the various resources used in the example. The source code for these resources is included after the
table.

Resource Resource Name Usage

Event files Component event (compEvent.evt) Defines the component and application events in
and application event (appEvent.evt) separate resources. eventsContainer.cmp
shows how to use both component and application
events.

Notifier Component (eventsNotifier.cmp) The notifier contains an onclick browser event to

and its controller initiate the event. The controller fires the event.
(eventsNotifierController.js)

Handler Component (eventsHandler.cmp) The handler component contains the notifier

and its controller component (or a <aura:handler> tag for
(eventsHandlerController.js) application events), and calls the controller action that
is executed after the event is fired.

Container Component eventsContainer.cmp Displays the event handlers on the UI for the complete
demo.

The definitions of component and application events are stored in separate .evt resources, but individual notifier and handler
component bundles can contain code to work with both types of events.
The component and application events both contain a context attribute that defines the shape of the event. This is the data that is
passed to handlers of the event.

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Component Event
Here is the markup for compEvent.evt.
<!--c:compEvent-->
<aura:event type="COMPONENT">
<!-- pass context of where the event was fired to the handler. -->
<aura:attribute name="context" type="String"/>
</aura:event>

Application Event
Here is the markup for appEvent.evt.
<!--c:appEvent-->
<aura:event type="APPLICATION">
<!-- pass context of where the event was fired to the handler. -->
<aura:attribute name="context" type="String"/>
</aura:event>

Notifier Component
The eventsNotifier.cmp notifier component contains buttons to initiate a component or application event.
The notifier uses aura:registerEvent tags to declare that it may fire the component and application events. Note that the
name attribute is required but the value is only relevant for the component event; the value is not used anywhere else for the application
event.
The parentName attribute is not set yet. We will see how this attribute is set and surfaced in eventsContainer.cmp.
<!--c:eventsNotifier-->
<aura:component>
<aura:attribute name="parentName" type="String"/>
<aura:registerEvent name="componentEventFired" type="c:compEvent"/>
<aura:registerEvent name="appEvent" type="c:appEvent"/>

<div>
<h3>This is {!v.parentName}'s eventsNotifier.cmp instance</h3>
<p><ui:button
label="Click here to fire a component event"
press="{!c.fireComponentEvent}" />
</p>
<p><ui:button
label="Click here to fire an application event"
press="{!c.fireApplicationEvent}" />
</p>
</div>
</aura:component>

CSS source
The CSS is in eventsNotifier.css.
/* eventsNotifier.css */
.cEventsNotifier {

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display: block;
margin: 10px;
padding: 10px;
border: 1px solid black;
}

Client-side controller source

The eventsNotifierController.js controller fires the event.
/* eventsNotifierController.js */
{
fireComponentEvent : function(cmp, event) {
var parentName = cmp.get("v.parentName");

// Look up event by name, not by type

var compEvents = cmp.getEvent("componentEventFired");

compEvents.setParams({ "context" : parentName });

compEvents.fire();
},

fireApplicationEvent : function(cmp, event) {

var parentName = cmp.get("v.parentName");

// note different syntax for getting application event

var appEvent = $A.get("e.c:appEvent");

appEvent.setParams({ "context" : parentName });

appEvent.fire();
}
}

You can click the buttons to fire component and application events but there is no change to the output because we haven't wired up
the handler component to react to the events yet.
The controller sets the context attribute of the component or application event to the parentName of the notifier component
before firing the event. We will see how this affects the output when we look at the handler component.

Handler Component
The eventsHandler.cmp handler component contains the c:eventsNotifier notifier component and <aura:handler>
tags for the application and component events.
<!--c:eventsHandler-->
<aura:component>
<aura:attribute name="name" type="String"/>
<aura:attribute name="mostRecentEvent" type="String" default="Most recent event handled:"/>

<aura:attribute name="numComponentEventsHandled" type="Integer" default="0"/>

<aura:attribute name="numApplicationEventsHandled" type="Integer" default="0"/>

<aura:handler event="c:appEvent" action="{!c.handleApplicationEventFired}"/>

<aura:handler name="componentEventFired" event="c:compEvent"
action="{!c.handleComponentEventFired}"/>

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<div>
<h3>This is {!v.name}</h3>
<p>{!v.mostRecentEvent}</p>
<p># component events handled: {!v.numComponentEventsHandled}</p>
<p># application events handled: {!v.numApplicationEventsHandled}</p>
<c:eventsNotifier parentName="{#v.name}" />
</div>
</aura:component>

Note: {#v.name} is an unbound expression. This means that any change to the value of the parentName attribute in
c:eventsNotifier doesn’t propagate back to affect the value of the name attribute in c:eventsHandler. For more
information, see Data Binding Between Components on page 27.
CSS source
The CSS is in eventsHandler.css.
/* eventsHandler.css */
.cEventsHandler {
display: block;
margin: 10px;
padding: 10px;
border: 1px solid black;
}

Client-side controller source

The client-side controller is in eventsHandlerController.js.
/* eventsHandlerController.js */
{
handleComponentEventFired : function(cmp, event) {
var context = event.getParam("context");
cmp.set("v.mostRecentEvent",
"Most recent event handled: COMPONENT event, from " + context);

var numComponentEventsHandled =
parseInt(cmp.get("v.numComponentEventsHandled")) + 1;
cmp.set("v.numComponentEventsHandled", numComponentEventsHandled);
},

handleApplicationEventFired : function(cmp, event) {

var context = event.getParam("context");
cmp.set("v.mostRecentEvent",
"Most recent event handled: APPLICATION event, from " + context);

var numApplicationEventsHandled =
parseInt(cmp.get("v.numApplicationEventsHandled")) + 1;
cmp.set("v.numApplicationEventsHandled", numApplicationEventsHandled);
}
}

The name attribute is not set yet. We will see how this attribute is set and surfaced in eventsContainer.cmp.

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Communicating with Events Firing Aura Events from Non-Aura Code

You can click buttons and the UI now changes to indicate the type of event. The click count increments to indicate whether it's a
component or application event. We aren't finished yet though. Notice that the source of the event is undefined as the event context
attribute hasn't been set .

Container Component
Here is the markup for eventsContainer.cmp.
<!--c:eventsContainer-->
<aura:component>
<c:eventsHandler name="eventsHandler1"/>
<c:eventsHandler name="eventsHandler2"/>
</aura:component>

The container component contains two handler components. It sets the name attribute of both handler components, which is passed
through to set the parentName attribute of the notifier components. This fills in the gaps in the UI text that we saw when we looked
at the notifier or handler components directly.
Navigate to the c:eventsContainer component.
http://localhost:<port>/c/eventsContainer.cmp.
Click the Click here to fire a component event button for either of the event handlers. Notice that the # component events handled
counter only increments for that component because only the firing component's handler is notified.
Click the Click here to fire an application event button for either of the event handlers. Notice that the # application events handled
counter increments for both the components this time because all the handling components are notified.

SEE ALSO:
Component Event Example
Application Event Example
Event Handling Lifecycle

Firing Aura Events from Non-Aura Code

You can fire Aura events from JavaScript code outside an Aura app. For example, your Aura app might need to call out to some non-Aura
code, and then have that code communicate back to your Aura app once it's done.
For example, you could call external code that needs to log into another system and return some data to your Aura app. Let's call this
event mynamespace:externalEvent. You'll fire this event when your non-Aura code is done by including this JavaScript in
your non-Aura code.
var myExternalEvent;
if(window.opener.$A &&
(myExternalEvent = window.opener.$A.get("e.mynamespace:externalEvent"))) {
myExternalEvent.setParams({isOauthed:true});
myExternalEvent.fire();
}

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Communicating with Events Events Best Practices

window.opener.$A.get() references the master window where your Aura app is loaded.

SEE ALSO:
Application Events
Modifying Components Outside the Framework Lifecycle

Events Best Practices

Here are some best practices for working with events.

Use Component Events Whenever Possible

Always try to use a component event instead of an application event, if possible. Component events can only be handled by components
above them in the containment hierarchy so their usage is more localized to the components that need to know about them. Application
events are best used for something that should be handled at the application level, such as navigating to a specific record. Application
events allow communication between components that are in separate parts of the application and have no direct containment
relationship.

Separate Low-Level Events from Business Logic Events

It's a good practice to handle low-level events, such as a click, in your event handler and refire them as higher-level events, such as an
approvalChange event or whatever is appropriate for your business logic.

Dynamic Actions based on Component State

If you need to invoke a different action on a click event depending on the state of the component, try this approach:
1. Store the component state as a discrete value, such as New or Pending, in a component attribute.
2. Put logic in your client-side controller to determine the next action to take.
3. If you need to reuse the logic in your component bundle, put the logic in the helper.
For example:
1. Your component markup contains <ui:button label="do something" press="{!c.click}" />.
2. In your controller, define the click function, which delegates to the appropriate helper function or potentially fires the correct
event.

Using a Dispatcher Component to Listen and Relay Events

If you have a large number of handler component instances listening for an event, it may be better to identify a dispatcher component
to listen for the event. The dispatcher component can perform some logic to decide which component instances should receive further
information and fire another component or application event targeted at those component instances.

SEE ALSO:
Handling Events with Client-Side Controllers
Events Anti-Patterns

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Communicating with Events Events Anti-Patterns

Events Anti-Patterns
These are some anti-patterns that you should avoid when using events.

Don't Fire an Event in a Renderer

Firing an event in a renderer can cause an infinite rendering loop.
Don’t do this!
afterRender: function(cmp, helper) {
this.superAfterRender();
$A.get("e.myns:mycmp").fire();
}

Instead, use the init hook to run a controller action after component construction but before rendering. Add this code to your
component:
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

For more details, see .Invoking Actions on Component Initialization on page 151.

Don’t Use onclick and ontouchend Events

You can’t use different actions for onclick and ontouchend events in a component. The framework translates touch-tap events
into clicks and activates any onclick handlers that are present.

SEE ALSO:
Create a Custom Renderer
Events Best Practices

Events Fired During the Rendering Lifecycle

A component is instantiated, rendered, and rerendered during its lifecycle. A component is rerendered only when there’s a programmatic
or value change that would require a rerender, such as when a browser event triggers an action that updates its data.

Component Creation
The component lifecycle starts when the client sends an HTTP request to the server and the component configuration data is returned
to the client. No server trip is made if the component definition is already on the client from a previous request and the component has
no server dependencies.
Let’s look at an app with several nested components. The framework instantiates the app and goes through the children of the v.body
facet to create each component, First, it creates the component definition, its entire parent hierarchy, and then creates the facets within
those components. The framework also creates any component dependencies on the server, including definitions for attributes, interfaces,
controllers, actions, and models.
For an abstract component, your JavaScript or Java provider determines which concrete implementation of the component to create.
The following image lists the order of component creation.

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Communicating with Events Events Fired During the Rendering Lifecycle

After creating a component instance, the serialized component definitions and instances are sent down to the client. Definitions are
cached but not the instance data. The client deserializes the response to create the JavaScript objects or maps, resulting in an instance
tree that’s used to render the component instance. When the component tree is ready, the init event is fired for all the components,
starting from the children component and finishing in the parent component.

Component Rendering
The rendering lifecycle happens once in the lifetime of a component unless the component gets explicitly unrendered. When you create
a component:
The following image depicts a typical rendering lifecycle of a component on the client, after the component definitions and instances
are deserialized.
1. The init event is fired by the component service that constructs the components to signal that initialization has completed.
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

You can customize the init handler and add your own controller logic before the component starts rendering. For more information,
see Invoking Actions on Component Initialization on page 151.
2. For each component in the tree, the base implementation of render() or your custom renderer is called to start component
rendering. For more information, see Create a Custom Renderer on page 163. Similar to the component creation process, rendering
starts at the root component, its children components and their super components, if any, and finally the subchildren components.
3. Once your components are rendered to the DOM, afterRender() is called to signal that rendering is completed for each of
these component definitions. It enables you to interact with the DOM tree after the framework rendering service has created the
DOM elements.
4. To indicate that the client is done waiting for a response to the server request XHR, the aura:doneWaiting event is fired. You
can handle this event by adding a handler wired to a client-side controller action.

Note: We don't recommend using the legacy aura:doneWaiting event except as a last resort. The
aura:doneWaiting application event is fired for every server response, even for responses from other components in
your app. Unless your component is running in complete isolation in a standalone app and not included in Lightning Experience
or the Salesforce app, you probably don’t want to handle this application event. The container app may fire server-side actions
and trigger your event handler multiple times.

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Communicating with Events System Events

5. The framework fires a render event, enabling you to interact with the DOM tree after the framework’s rendering service has
inserted DOM elements. Handling the render event is preferred to creating a custom renderer and overriding afterRender().
For more information, see Handle the render Event.
6. Finally, the aura:doneRendering event is fired at the end of the rendering lifecycle.

Note: We don't recommend using the legacy aura:doneRendering event except as a last resort. Unless your component
is running in complete isolation in a standalone app and not included in complex apps, such as Lightning Experience or the
Salesforce app, you probably don’t want to handle this application event. The container app may trigger your event handler
multiple times.

Rendering Nested Components

Let’s say that you have an app myApp.app that contains a component myCmp.cmp with a ui:button component.

During initialization, the init() event is fired in this order: ui:button, ui:myCmp, and myApp.app.

SEE ALSO:
Create a Custom Renderer
Server-Side Processing for Component Requests
Client-Side Processing for Component Requests
System Event Reference

System Events
The framework fires several system events during its lifecycle.
You can handle these events in your Lightning apps or components, and within the Salesforce mobile app.

Event Name Description

aura:doneRendering Indicates that the initial rendering of the root application has completed. We
don't recommend using the legacy aura:doneRendering event except
as a last resort. Unless your component is running in complete isolation in a
standalone app and not included in complex apps, such as Lightning Experience
or the Salesforce app, you probably don’t want to handle this application event.
The container app may trigger your event handler multiple times.

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Event Name Description

aura:doneWaiting Indicates that the app is done waiting for a response to a server request. This
event is preceded by an aura:waiting event. We don't recommend using
the legacy aura:doneWaiting event except as a last resort. The
aura:doneWaiting application event is fired for every server response,
even for responses from other components in your app. Unless your component
is running in complete isolation in a standalone app and not included in Lightning
Experience or the Salesforce app, you probably don’t want to handle this
application event. The container app may fire server-side actions and trigger your
event handler multiple times.

aura:locationChange Indicates that the hash part of the URL has changed.

aura:noAccess Indicates that a requested resource is not accessible due to security constraints
on that resource.

aura:systemError Indicates that an error has occurred.

aura:valueChange Indicates that an attribute value has changed.

aura:valueDestroy Indicates that a component has been destroyed.

aura:valueInit Indicates that an app or component has been initialized.

aura:valueRender Indicates that an app or component has been rendered or rerendered.

aura:waiting Indicates that the app is waiting for a response to a server request. We don't
recommend using the legacy aura:waiting event except as a last resort.
The aura:waiting application event is fired for every server request, even
for requests from other components in your app. Unless your component is
running in complete isolation in a standalone app and not included in Lightning
Experience or the Salesforce app, you probably don’t want to handle this
application event. The container app may fire server-side actions and trigger your
event handler multiple times.

SEE ALSO:
System Event Reference

130
CHAPTER 5 Creating Apps
In this chapter ... Components are the building blocks of an app. This section shows you a typical workflow to put the
pieces together to create a new app.
• App Overview
• Designing App UI
• Creating App
Templates
• Developing Secure
Code
• Styling Apps
• Using JavaScript
• JavaScript Cookbook
• Using Java
• Java Cookbook
• Lightning Container
• Controlling Access
• URL-Centric
Navigation
• Using
Object-Oriented
Development
• Caching with Storage
Service
• Using the AppCache

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Creating Apps App Overview

App Overview
An app is a special top-level component whose markup is in a .app file.
On a production server, the .app file is the only addressable unit in a browser URL. Access an app using the URL:
http://<myServer>/<namespace>/<appName>.app

Note: You can access components directly in a browser URL in DEV mode by using the component's .cmp extension.

SEE ALSO:
aura:application
Supported HTML Tags

Designing App UI
Design your app's UI by including markup in the .app resource. Each part of your UI corresponds to a component, which can in turn
contain nested components. Compose components to create a sophisticated app.
An app’s markup starts with the <aura:application> tag.

Note: To learn more about the <aura:application> tag, see aura:application.

Let's look at a sample.app file, which starts with the <aura:application> tag.
<aura:application extends="force:slds">
<lightning:layout>
<lightning:layoutItem padding="around-large">
<h1 class="slds-text-heading_large">Sample App</h1>
</lightning:layoutItem>
</lightning:layout>
<lightning:layout>
<lightning:layoutItem padding="around-small">
Sidebar
<!-- Other component markup here -->
</lightning:layoutItem>
<lightning:layoutItem padding="around-small">
Content
<!-- Other component markup here -->
</lightning:layoutItem>
</lightning:layout>

</aura:application>

The sample.app file contains HTML tags, such as <h1>, as well as components, such as <lightning:layout>. We won't go
into the details for all the components here but note how simple the markup is. The <lightning:layoutItem> component
can contain other components or HTML markup.

SEE ALSO:
aura:application

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Creating Apps Creating App Templates

Creating App Templates

An app template bootstraps the loading of the framework and the app. Customize an app’s template by creating a component that
extends the default aura:template template.
A template must have the isTemplate system attribute in the <aura:component> tag set to true. This informs the framework
to allow restricted items, such as <script> tags, which aren't allowed in regular components.
For example, a sample app has a np:template template that extends aura:template. np:template looks like:
<aura:component isTemplate="true" extends="aura:template">
<aura:set attribute="title" value="My App"/>
...
</aura:component>

Note how the component extends aura:template and sets the title attribute using aura:set.
The app points at the custom template by setting the template system attribute in <aura:application>.
<aura:application template="np:template">
...
</aura:application>

A template can only extend a component or another template. A component or an application can't extend a template.

JavaScript Libraries
You can reference a JavaScript library in your app's template. For other options, see Using External JavaScript Libraries on page 154.
To add a JavaScript library to your app’s template, use aura:set to set the extraScriptTags attribute in the template
component. This sets the extraScriptTags attribute in aura:template, which your app's template extends.
This sample template markup references a third-party JavaScript library.
<aura:set attribute="extraScriptTags">
<script type="text/javascript" src="/aura/codemirror/codemirror.js"></script>
</aura:set>

You can use multiple <script> tags to include more than one library. For example:
<aura:set attribute="extraScriptTags">
<script type="text/javascript" src="/aura/codemirror/codemirror.js"></script>
<script type="text/javascript" src="/aura/otherLib/otherLib.js"></script>
</aura:set>

External CSS
To use an external style sheet, you must link to it in your app's template. Use aura:set to set the extraStyleTags attribute in
the template component. This sets the extraStyleTags attribute in aura:template, which your app's template extends.
For example:
<aura:set attribute="extraStyleTags">
<link href="/aura/external/google-code-prettify/prettify.css" rel="stylesheet"
type="text/css" />
</aura:set>

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You can link to multiple external style sheets. For example:

<aura:set attribute="extraStyleTags">
<link href="/aura/external/google-code-prettify/prettify.css" rel="stylesheet"
type="text/css" />
<link href="/aura/external/morecss/morecss.css" rel="stylesheet" type="text/css"
/>
</aura:set>

You can also use inline style in your template, but we recommend using an external style sheet instead. To use inline style, use aura:set
to set the inlineStyle attribute in the template component. For example:
<aura:set attribute="inlineStyle">
<style>
body {
background-color: #6cc4e3;
}
</style>
</aura:set>

SEE ALSO:
aura:application
CSS in Components
Using External JavaScript Libraries

Developing Secure Code

The LockerService architectural layer enhances security by isolating individual Lightning components in their own containers and
enforcing coding best practices.

IN THIS SECTION:
What is LockerService?
LockerService is a powerful security architecture for Lightning components. LockerService enhances security by isolating Lightning
components in their own namespace. LockerService also promotes best practices that improve the supportability of your code by
only allowing access to supported APIs and eliminating access to non-published framework internals.

What is LockerService?
LockerService is a powerful security architecture for Lightning components. LockerService enhances security by isolating Lightning
components in their own namespace. LockerService also promotes best practices that improve the supportability of your code by only
allowing access to supported APIs and eliminating access to non-published framework internals.

IN THIS SECTION:
JavaScript ES5 Strict Mode Enforcement
LockerService implicitly enables JavaScript ES5 strict mode. You don’t need to specify "use strict" in your code. JavaScript
strict mode makes code more robust and supportable. For example, it throws some errors that would otherwise be suppressed.

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Creating Apps What is LockerService?

DOM Access Containment

A component can only traverse the DOM and access elements created by a component in the same namespace. This behavior
prevents the anti-pattern of reaching into DOM elements owned by components in another namespace.
Secure Wrappers for Global References
LockerService applies restrictions to global references. LockerService provides secure versions of non-intrinsic objects, such as
window. For example, the secure version of window is SecureWindow. You can interact with a secure wrapper in the same
way as you interact with the non-intrinsic object, but the secure wrappers filter access to the object and its properties. The secure
wrappers expose a subset of the API of the underlying objects.
Access to Supported JavaScript API Framework Methods Only
You can access published, supported JavaScript API framework methods only. These methods are published in the reference doc
app at http://<myServer>/auradocs/reference.app. Previously, unsupported methods were accessible, which
exposed your code to the risk of breaking when unsupported methods were changed or removed.

JavaScript ES5 Strict Mode Enforcement

LockerService implicitly enables JavaScript ES5 strict mode. You don’t need to specify "use strict" in your code. JavaScript strict
mode makes code more robust and supportable. For example, it throws some errors that would otherwise be suppressed.
A few common stumbling points when using strict mode are:
• You must declare variables with the var keyword.
• You must explicitly attach a variable to the window object to make the variable available outside a library.
• The libraries that your components use must also work in strict mode.
For more information about JavaScript strict mode, see the Mozilla Developer Network.

DOM Access Containment

A component can only traverse the DOM and access elements created by a component in the same namespace. This behavior prevents
the anti-pattern of reaching into DOM elements owned by components in another namespace.

Note: It’s an anti-pattern for any component to “reach into” another component, regardless of namespace. LockerService only
prevents cross-namespace access. Your good judgment should prevent cross-component access within your own namespace as
it makes components tightly coupled and more likely to break.
Let’s look at a sample component that demonstrates DOM containment.
<!--c:domLocker-->
<aura:component>
<div id="myDiv" aura:id="div1">
<p>See how LockerService restricts DOM access</p>
</div>
<lightning:button name="myButton" label="Peek in DOM"
aura:id="button1" onclick="{!c.peekInDom}"/>
</aura:component>

The c:domLocker component creates a <div> element and a <lightning:button> component.

Here’s the client-side controller that peeks around in the DOM.
({ /* domLockerController.js */
peekInDom : function(cmp, event, helper) {
console.log("cmp.getElements(): ", cmp.getElements());

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Creating Apps What is LockerService?

// access the DOM in c:domLocker

console.log("div1: ", cmp.find("div1").getElement());
console.log("button1: ", cmp.find("button1"));
console.log("button name: ", event.getSource().get("v.name"));

// returns an error
//console.log("button1 element: ", cmp.find("button1").getElement());
}
})

Valid DOM Access

The following methods are valid DOM access because the elements are created by c:domLocker.
cmp.getElements()
Returns the elements in the DOM rendered by the component.
cmp.find()
Returns the div and button components, identified by their aura:id attributes.
cmp.find("div1").getElement()
Returns the DOM element for the div as c:domLocker created the div.
event.getSource().get("v.name")
Returns the name of the button that dispatched the event; in this case, myButton.

Invalid DOM Access

You can’t use cmp.find("button1").getElement() to access the DOM element created by <lightning:button>.
LockerService doesn’t allow c:domLocker to access the DOM for <lightning:button> because the button is in the
lightning namespace and c:domLocker is in the c namespace.
If you uncomment the code for cmp.find("button1").getElement(), you’ll see an error:
c:domLocker$controller$peekInDom [cmp.find(...).getElement is not a function]

IN THIS SECTION:
How LockerService Uses the Proxy Object
LockerService uses the standard JavaScript Proxy object to filter a component’s access to underlying JavaScript objects. The
Proxy object ensures that a component only sees DOM elements created by a component in the same namespace.

How LockerService Uses the Proxy Object

LockerService uses the standard JavaScript Proxy object to filter a component’s access to underlying JavaScript objects. The Proxy
object ensures that a component only sees DOM elements created by a component in the same namespace.
You can interact with a Proxy object in the same way as you interact with the raw JavaScript object, but the object shows up in the
browser’s console as a Proxy. It’s useful to understand LockerService’s usage of Proxy if you drop into your browser’s debugger and
start poking around.
When a component creates an intrinsic JavaScript object, LockerService returns the raw JavaScript object. When LockerService filters
the object, it returns a Proxy object. Some scenarios where LockerService filters an object and returns a Proxy object are:
• Passing an object to a component in a different namespace.

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• Calling cmp.get() to retrieve an attribute value that you set with the value of a native JavaScript object or array. The object or
array isn’t filtered when it’s originally created.
When you access these objects, LockerService returns a Proxy object.
• Any object that implements the HTMLCollection interface
• A SecureElement object, which represents an HTML element.
For more information about standard JavaScript Proxy object, see the Mozilla Developer Network.

Secure Wrappers for Global References

LockerService applies restrictions to global references. LockerService provides secure versions of non-intrinsic objects, such as window.
For example, the secure version of window is SecureWindow. You can interact with a secure wrapper in the same way as you
interact with the non-intrinsic object, but the secure wrappers filter access to the object and its properties. The secure wrappers expose
a subset of the API of the underlying objects.
Here’s a list of the secure objects that you’ll most commonly encounter.
SecureAura
Secure wrapper for $A, which is the entry point for using the framework in JavaScript code.
SecureComponent
Secure wrapper for the Component object.
SecureComponentRef
SecureComponentRef is a subset of SecureComponent that provides the external API for a component in a different
namespace.
When you’re in a controller or helper, you have access to a SecureComponent, essentially the this object. In other contexts
when you’re working with a component, you get a SecureComponentRef instead if you reference a component in a different
namespace. For example, if your markup includes a lightning:button and you call cmp.find("buttonAuraId"),
you get a SecureComponentRef as lightning:button is in a different namespace from the component containing
the button markup.
SecureDocument
Secure wrapper for the Document object, which represents the root node of the HTML document or page. The Document
object is the entry point into the page’s content, which is the DOM tree.
SecureElement
Secure wrapper for the Element object, which represents an HTML element. SecureElement is wrapped in a Proxy object
as a performance optimization so that its data can be lazily filtered when it’s accessed. The HTML element is represented by a Proxy
object if you’re debugging in the browser console.
SecureObject
Secure wrapper for an object that is wrapped by LockerService. When you see a SecureObject, it typically means you don’t
have access to the object so some properties aren’t available.
SecureWindow
Secure wrapper for the Window object, which represents a window containing a DOM document.

Example
Let’s look at a sample component that demonstrates some of the secure wrappers.
<!--c:secureWrappers-->
<aura:component >

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<div id="myDiv" aura:id="div1">

<p>See how LockerService uses secure wrappers</p>
</div>
<lightning:button name="myButton" label="Peek in DOM"
aura:id="button1" onclick="{!c.peekInDom}"/>
</aura:component>

The c:secureWrappers component creates a <div> HTML element and a <lightning:button> component.
Here’s the client-side controller that peeks around in the DOM.
({ /* secureWrappersController.js */
peekInDom : function(cmp, event, helper) {
console.log("div1: ", cmp.find("div1").getElement());

console.log("button1: ", cmp.find("button1"));

console.log("button name: ", event.getSource().get("v.name"));
// add debugger statement for inspection
// always remove this from production code
debugger;
}
})

We use console.log() to look at the <div> element and the button. The <div> SecureElement is wrapped in a Proxy
object as a performance optimization so that its data can be lazily filtered when it’s accessed.
We put a debugger statement in the code so that we could inspect the elements in the browser console.
Type these expressions into the browser console and look at the results.
cmp
cmp+""
cmp.find("button1")
cmp.find("button1")+""
window
window+""
$A
$A+""

We add an empty string to some expressions so that the object is converted to a String. You could also use the toString()
method.
Here’s the output.

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Let’s examine some of the output.

cmp+""
Returns a SecureComponent object for cmp, which represents the c:secureWrappers component.
cmp.find("button1")+""
Returns a SecureComponentRef, which represents the external API for a component in a different namespace. In this example,
the component is lightning:button.
window+""
Returns a SecureWindow object.
$A+""
Returns a SecureAura object.

IN THIS SECTION:
JavaScript API for Secure Wrappers
The secure wrappers, such as SecureWindow, expose a subset of the API of the objects that they wrap. The API for the secure
wrappers is documented in the LockerService API Viewer app or the reference doc app.

SEE ALSO:
How LockerService Uses the Proxy Object

JavaScript API for Secure Wrappers

The secure wrappers, such as SecureWindow, expose a subset of the API of the objects that they wrap. The API for the secure wrappers
is documented in the LockerService API Viewer app or the reference doc app.

LockerService API Viewer

The LockerService API Viewer shows the DOM APIs exposed by LockerService versus the standard DOM APIs. The API Viewer app lists
the API for SecureDocument, SecureElement, and SecureWindow.
The API Viewer lets you quickly see the difference between the standard DOM APIs and the LockerService APIs.
• An orange row indicates an API that behaves differently in LockerService.

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• A red row means the API isn’t supported in LockerService.

Reference Doc App

The reference doc app lists the API for SecureComponent under JavaScript API > Component.
SecureAura is the wrapper for $A.

SEE ALSO:
Secure Wrappers for Global References

Access to Supported JavaScript API Framework Methods Only

You can access published, supported JavaScript API framework methods only. These methods are published in the reference doc app
at http://<myServer>/auradocs/reference.app. Previously, unsupported methods were accessible, which exposed
your code to the risk of breaking when unsupported methods were changed or removed.

Styling Apps
An app is a special top-level component whose markup is in a .app resource. Just like any other component, you can put CSS in its
bundle in a resource called <appName>.css.
For example, if the app markup is in notes.app, its CSS is in notes.css.
Besides CSS that styles the component in the bundle, you can add a flavor CSS file using the file name
<componentName>Flavors.css. Flavors enable you to style different component instances easily and apply various styles to
components within a namespace.

IN THIS SECTION:
Using External CSS
To use external CSS in your app, add it to your app’s template.
More Readable Styling Markup with the join Expression
Markup can get messy when you specify the class names to apply based on the component attribute values. Try using a join
expression for easier-to-read markup.
Styling with Flavors
A flavor provides stylistic variations of a component. Each flavor is essentially a CSS class that can apply varying styles to different
instances of a components.
Styling with Tokens
Tokens make it easy to ensure that your design is consistent, and even easier to update it as your design evolves. Define the token
values once and reuse them throughout your Aura applications.

SEE ALSO:
CSS in Components
Creating App Templates
Add Lightning Components as Custom Tabs in the Salesforce App

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Creating Apps Using External CSS

Using External CSS

To use external CSS in your app, add it to your app’s template.

SEE ALSO:
Using External JavaScript Libraries

More Readable Styling Markup with the join Expression

Markup can get messy when you specify the class names to apply based on the component attribute values. Try using a join expression
for easier-to-read markup.
This example sets the class names based on the component attribute values. It’s readable, but the spaces between class names are easy
to forget.
<li class="{! 'calendarEvent ' +
v.zoomDirection + ' ' +
(v.past ? 'pastEvent ' : '') +
(v.zoomed ? 'zoom ' : '') +
(v.multiDayFragment ? 'multiDayFragment ' : '')}">
<!-- content here -->
</li>

Sometimes, if the markup is not broken into multiple lines, it can hurt your eyes or make you mutter profanities under your breath.
<li class="{! 'calendarEvent ' + v.zoomDirection + ' ' + (v.past ? 'pastEvent ' : '') +
(v.zoomed ? 'zoom ' : '') + (v.multiDayFragment ? 'multiDayFragment ' : '')}">
<!-- content here -->
</li>

Try using a join expression instead for easier-to-read markup. This example join expression sets ' ' as the first argument so that
you don’t have to specify it for each subsequent argument in the expression.
<li
class="{! join(' ',
'calendarEvent',
v.zoomDirection,
v.past ? 'pastEvent' : '',
v.zoomed ? 'zoom' : '',
v.multiDayFragment ? 'multiDayFragment' : ''
)}">
<!-- content here -->
</li>

You can also use a join expression for dynamic styling.

<div style="{! join(';',
'top:' + v.timeOffsetTop + '%',
'left:' + v.timeOffsetLeft + '%',
'width:' + v.timeOffsetWidth + '%'
)}">

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<!-- content here -->

</div>

SEE ALSO:
Expression Functions Reference

Vendor Prefixes
Vendor prefixes, such as —moz- and —webkit- among many others, are automatically added in Aura.
You only need to write the unprefixed version, and the framework automatically adds any prefixes that are necessary when generating
the CSS output. If you choose to add them, they are used as-is. This enables you to specify alternative values for certain prefixes.

Example: For example, this is an unprefixed version of border-radius.

.class {
border-radius: 2px;
}

The previous declaration results in the following declarations.

.class {
-webkit-border-radius: 2px;
-moz-border-radius: 2px;
border-radius: 2px;
}

Styling with Flavors

A flavor provides stylistic variations of a component. Each flavor is essentially a CSS class that can apply varying styles to different instances
of a components.
Styling with flavors enables you to restyle the original components easily, but also avoid overriding any previous styling. When creating
flavors, create them at the component level in component bundles.
To use flavors, you must make a component flavorable. Specify aura:flavorable="true" on the HTML element that should
receive the flavor class name:
<aura:component>
<div aura:flavorable="true">
//other markup here
</div>
</aura:component>

Only one element is marked flavorable, and it doesn't have to be a top-level element. For an example, see the ui:button component.

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Creating and Setting a Flavor

You can create one or more flavors in a component bundle. Use the file name <componentName>Flavors.css to wire up the
flavors to your component. Note that this CSS file for flavors is different than your regular <componentName>.css file. In the flavor
CSS file, create your flavor in the format .THIS--flavorName. Each selector must be scoped by the flavor name class selector.
.THIS--info, .THIS--warning {
border: 1px solid #eee;
margin: t(margin);
}

.THIS--info { background-color: blue }

.THIS--warning { background-color: yellow }

When creating flavors for a component, move the existing CSS into the default flavor, if possible. The default flavor should be referenced
using .THIS, which automatically converts to .THIS--default. For an example, see the ui:button component.

Note: Flavors are applied to an element if it matches the designated or default flavor of the component. When using flavors, we
recommend applying little or no CSS in the regular CSS file, and using at least a default flavor in the flavor CSS file.
You can specify different flavor names. For example:
<!-- myComponent.cmp -->
<aura:component defaultFlavor="alternative">
<div aura:flavorable="true">
//other markup here
</div>
</aura:component>

/* myComponentFlavors.css */
.THIS { color: red }
.THIS--alternative { color: green }

Setting a Flavor on Component Instances

When multiple flavors are available for a component, you can specify which one to use. For example:
<ui:button label="Search"/>
<ui:button aura:flavor="primary" label="Submit"/>

Specified flavors are not inherited or passed down to children.

You can specify multiple flavors on the same component instance by providing a comma-separated list of flavors in the aura:flavor
attribute.
<ui:button aura:flavor="default, brand" label="Submit"/>

Make sure the flavors you specify work together for the component.

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IN THIS SECTION:
Applying Flavors to a Namespace
You can add flavors for other components within your namespace.

SEE ALSO:
Dynamically Creating Components

Applying Flavors to a Namespace

You can add flavors for other components within your namespace.
Add flavors for components in another namespace in the flavors bundle (i.e., folder) within your own namespace. Create one flavored
CSS file per component you want to flavor, in the format of namespace-componentNameFlavors.css, where namespace is
the namespace of the component being flavored. For example, to create flavors for the ui:button component, create the CSS file
components/myNamespace/flavors/ui-buttonFlavors.css.

<!-- ui/button/button.cmp -->

<aura:component>
<button aura:flavorable="true">{!v.body}</button>
</aura:component>

/* ui/button/buttonFlavors.css */
.THIS {
color: red;
text-shadow: red 0 -2px;
}

/* sample/flavors/ui-buttonFlavors.css */
.THIS { color: green }
.THIS--special { font-weight: bold }

To apply the default and special flavors in the previous example, add a .flavors file to an application bundle. The next example
adds flavors specified in ui-buttonFlcavors.css to all ui:button component instances in an application.
<!-- myApp.flavors -->
<aura:flavors>
<aura:include source="sample:flavors"/>
</aura:flavors>

In this case, the default flavor of button will now be green, without affecting the text-shadow rule in the original flavor. By adding
the .flavors file to the application bundle, the special flavor is now available for the component.

Styling with Tokens

Tokens make it easy to ensure that your design is consistent, and even easier to update it as your design evolves. Define the token values
once and reuse them throughout your Aura applications.
There are two types of tokens: design tokens and configuration tokens.
Design Tokens
Design tokens are visual design “atoms” for building a design for your components or apps. Specifically, they’re named entities that
store visual design attributes, such as pixel values for margins and spacing, font sizes and families, or hex values for colors. Use design
tokens in CSS.

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Capture the essential values of your visual design into named tokens. Tokens are a terrific way to centralize the low-level values,
which you then use to compose the styles that make up the design of your component or app.
Configuration Tokens
Use configuration tokens in expressions, such as in component markup, for cross-cutting application values that remain consistent
across all components in your app. A typical use case for configuration tokens is in a markup expression setting a class name.
It’s a best practice to separate design tokens and configuration tokens into separate tokens bundles. However, the separation isn’t
enforced so you have freedom to create a token structure that works for you.

IN THIS SECTION:
Tokens Bundles
Tokens are a type of bundle, just like components, events, and interfaces. A tokens bundle only contains a tokens file.
Defining Tokens
A token is a name-value pair that you specify using the <aura:token> tag. A tokens file contains one or more tokens.
Using Design Tokens in CSS
Use tokens in your component’s CSS for consistent styling across all components in your app.
Using Configuration Tokens in Expressions
Use configuration tokens in expressions, such as in component markup, for cross-cutting application values that remain consistent
across all components in your app. A typical use case for configuration tokens is in a markup expression setting a class name.

Tokens Bundles
Tokens are a type of bundle, just like components, events, and interfaces. A tokens bundle only contains a tokens file.

CSS Tokens Bundle for a Namespace

The tokens file for a namespace is automatically loaded for usage in CSS if it follows this file naming convention:
<myNamespace>/<myNamespace>Namespace/<myNamespace>Namespace.tokens
That's a little confusing. Let's look at an example with the docsample namespace. The CSS tokens file is located at:
aura-components/components/docsample/docsampleNamespace/docsampleNamespace.tokens
If this file exists, the tokens can be used in any CSS files in the docsample namespace.

Custom Tokens Bundles

You can have multiple token bundles and you can name them whatever you want. You must manually wire up your custom token files.
You might want a custom tokens bundle for an application so that you can use tokens in markup or other expressions. For example:
aura-components/components/docsample/myApp/myApp.tokens
Wire up the custom tokens file in your application by using the tokens attribute in your <aura:application> tag:
<aura:application tokens="docsample:myApp">
…
</aura:application>

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Use comma-separated values for multiple tokens files. The naming convention for automatically loading tokens for a namespace is
required for tokens in CSS, but can be augmented or overridden by using explicit token files. To use tokens in markup, you must explicitly
set the tokens file in the tokens attribute. For example:
<aura:application tokens="docsample:myApp,docsample:docsampleNamespace">
…
</aura:application>

Defining Tokens
A token is a name-value pair that you specify using the <aura:token> tag. A tokens file contains one or more tokens.
A tokens file starts with the <aura:tokens> tag. It can only contain <aura:token> tags to define tokens. The only allowed
attributes for the <aura:token> tag are name and value.
For example:
<aura:tokens>
<aura:token name="myBodyTextFontFace"
value="'Helvetica, Arial, sans-serif"/>
<aura:token name="myBodyTextFontWeight" value="normal"/>
<aura:token name="myBackgroundColor" value="#f4f6f9"/>
<aura:token name="myDefaultMargin" value="6px"/>
</aura:tokens>

IN THIS SECTION:
Using Expressions in Tokens Bundles
Tokens support a restricted set of expressions. Use expressions to reuse one token value in another token, or to combine tokens to
form a more complex style property.

Using Expressions in Tokens Bundles

Tokens support a restricted set of expressions. Use expressions to reuse one token value in another token, or to combine tokens to form
a more complex style property.

Cross-Referencing Tokens
To reference one token’s value in another token’s definition, wrap the token to be referenced in standard expression syntax.
In the following example, we look at two tokens files. baseApp.tokens defines some tokens. extendApp.tokens extends
baseApp.tokens and uses expressions to reference the tokens from baseApp.tokens.

<!-- baseApp.tokens -->

<aura:tokens>
...
<aura:token name="colorBackground" value="rgb(244, 246, 249)" />
<aura:token name="fontFamily" value="'Salesforce Sans', Arial, sans-serif" />
...
</aura:tokens>

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You can reference the tokens from baseApp.tokens in extendApp.tokens.

<!-- extendApp.tokens -->
<aura:tokens extends="docsample:baseApp">
<aura:token name="mainColor" value="{! colorBackground }" />
<aura:token name="btnColor" value="{! mainColor }" />
<aura:token name="myFont" value="{! fontFamily }" />
</aura:tokens>

The mainColor token in extendApp.tokens uses an expression to reference the colorBackground token in
baseApp.tokens.
You can only cross-reference tokens defined in the same file or a file you’re extending.
Expression syntax in tokens files is restricted to references to other tokens.

Combining Tokens
To support combining individual token values into more complex CSS style properties, the token() function supports string
concatenation. For example, if you have the following tokens defined:
<!-- myApp.tokens -->
<aura:tokens>
<aura:token name="defaultHorizonalSpacing" value="12px" />
<aura:token name="defaultVerticalSpacing" value="6px" />
</aura:tokens>

You can combine these two tokens in a CSS style definition. For example:
/* myComponent.css */
.THIS div.notification {
margin: token(defaultVerticalSpacing + ' ' + defaultHorizonalSpacing);
/* more styles here */
}

You can mix tokens with strings as much as necessary to create the right style definition. For example, use margin:
token(defaultVerticalSpacing + ' ' + defaultHorizonalSpacing + ' 3px'); to hard code the bottom
spacing in the preceding definition.
The only operator supported within the token() function is “+” for string concatenation.

SEE ALSO:
Using Expressions

Using Design Tokens in CSS

Use tokens in your component’s CSS for consistent styling across all components in your app.
To use a design token in a CSS file, reference it using the token(tokenName) function. For example:

.THIS p {
font-family: token(myBodyTextFontFace);
font-weight: token(myBodyTextFontWeight);
}

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myBodyTextFontFace corresponds to the name attribute in an <aura:token> definition. The

token(myBodyTextFontFace) function is replaced by the value in the <aura:token> definition.
If you prefer a more concise function name for referencing tokens, you can use the t() function instead of token(). The two are
equivalent.

SEE ALSO:
CSS in Components

Using Configuration Tokens in Expressions

Use configuration tokens in expressions, such as in component markup, for cross-cutting application values that remain consistent across
all components in your app. A typical use case for configuration tokens is in a markup expression setting a class name.
To use a token in markup, reference it using the token('tokenName') function. Note the single quotes around the token name.
This syntax differs from CSS usage where there are no single quotes around the token name.
For example:
<ui:label class="{!token('labelClass')}" />

labelClass corresponds to the name attribute in an <aura:token> definition.

Note: To use a token in an expression:

• The <aura:tokens> tag in the tokens bundle containing the token must set the attribute serialize="true". This
isn’t necessary for token usage in CSS as the CSS is parsed on the server before being serialized to the client. For example:
<aura:tokens serialize="true">
<aura:token name="labelClass" value="'sampleClass"/>
</aura:tokens>

• The <aura:application> tag must use the tokens attribute to point to the tokens bundle. For example:
<aura:application tokens="docsample:docsampleNamespace">

Let’s look at a complete sample. The docsample/docsampleNamespace/docsampleNamespace.tokens file defines

a few tokens.
<aura:tokens serialize="true">
<aura:token name="myBackgroundColor" value="#ff0000"/>
<aura:token name="other" value="notFirst"/>
</aura:tokens>

We’ll see how these tokens are used soon in CSS and markup. Notice that the <aura:tokens> tag sets serialize="true".
The docsample:tokensUsage component includes the {!token('other')} tag to reference the other token.
<!--docsample:tokensUsage-->
<aura:component>
<div class="white">
Hello, HTML!
</div>
<h2>Check out the style in this list.</h2>
<ul>
<li class="first">I'm first.</li>

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<li class="{!token('other')}">I'm second.</li>

<!--<li class="notFirst">I'm second.</li>-->
<li>I'm third.</li>
</ul>
</aura:component>

<li class="{!token('other')}">I'm second.</li> uses a token instead of the hard-coded equivalent that is
commented out:
<!--<li class="notFirst">I'm second.</li>-->

Here is the CSS.

/* docsample/tokensUsage.css*/
.THIS {
background-color: grey;
}
.THIS.white {
background-color: white;
}
.THIS .first {
background-color: token(myBackgroundColor);
}
.THIS .notFirst {
background-color: blue;
}

The .THIS .first selector uses token(myBackgroundColor) to set the background color for a list item in the markup.
myBackgroundColor is set to #ff0000 in docsampleNamespace.tokens.

<li class="first">I'm first.</li>

The second list item in the markup uses the other token.
<li class="{!token('other')}">I'm second.</li>

The value of the other token is set in docsampleNamespace.tokens.

<aura:token name="other" value="notFirst"/>

The .THIS .notFirst CSS selector sets the background color for this list item to blue.
Finally, let’s look at the app that loads the tokens file.
<!--docsample:wrapperApp-->
<aura:application tokens="docsample:docsampleNamespace">
<docsample:tokensUsage />
</aura:application>

The tokens attribute loads the tokens file at docsample/docsampleNamespace/docsampleNamespace.tokens.

After starting your server, navigate to the app at:
http://localhost:<port>/docsample/wrapperApp.app
The output should look like this.

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Creating Apps Using JavaScript

SEE ALSO:
Using Expressions
Defining Tokens

Using JavaScript
Use JavaScript for client-side code. The $A namespace is the entry point for using the framework in JavaScript code.
For all the methods available in $A, see the JavaScript API.
A component bundle can contain JavaScript code in a client-side controller, renderer, helper, or test file. Client-side controllers are the
most commonly used of these JavaScript files.

Publicly Accessible JavaScript Methods

The JavaScript API Reference lists the methods for each JavaScript object. When you are writing code, it's important to understand which
methods are publicly accessible for a JavaScript object.
A publicly accessible method is annotated with @export. Any method that doesn’t have an @export annotation is for internal use
by the framework.

Expressions in JavaScript Code

In JavaScript, use string syntax to evaluate an expression. For example, this expression retrieves the label attribute in a component.
var theLabel = cmp.get("v.label");

Note: Only use the {! } expression syntax in markup in .app or .cmp files.

IN THIS SECTION:
Invoking Actions on Component Initialization
Use the init event to initialize a component or fire an event after component construction but before rendering.
Sharing JavaScript Code in a Component Bundle
Put functions that you want to reuse in the component’s helper. Helper functions also enable specialization of tasks, such as processing
data and firing server-side actions.
Using External JavaScript Libraries
To use an external JavaScript library in your apps, include a <script> tag in your .app file or include it in your app’s template.
Creating Reusable JavaScript Libraries
An Aura JavaScript library enables you to create a set of JavaScript files that can be used by any component that imports the library.

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Working with Attribute Values in JavaScript

These are useful and common patterns for working with attribute values in JavaScript.
Working with a Component Body in JavaScript
These are useful and common patterns for working with a component’s body in JavaScript.
Working with Events in JavaScript
These are useful and common patterns for working with events in JavaScript.
Modifying the DOM
The Document Object Model (DOM) is the language-independent model for representing and interacting with objects in HTML and
XML documents. It’s important to know how to modify the DOM safely so that the framework’s rendering service doesn’t stomp on
your changes and give you unexpected results.
Client-Side Runtime Binding of Components
A provider enables you to use an abstract component in markup. The framework uses the provider to determine the concrete
component to use at runtime.
Checking Component Validity
If you navigate elsewhere in the UI while asynchronous code is executing, the framework unrenders and destroys the component
that made the asynchronous request. You can still have a reference to that component, but it is no longer valid. The
cmp.isValid() call returns false for an invalid component.
Modifying Components Outside the Framework Lifecycle
Use $A.getCallback() to wrap any code that modifies a component outside the normal rerendering lifecycle, such as in a
setTimeout() call. The $A.getCallback() call ensures that the framework rerenders the modified component and
processes any enqueued actions.
Validating Fields
Validate user input, handle errors, and display error messages on input fields.
Throwing and Handling Errors
The framework gives you flexibility in handling unrecoverable and recoverable app errors in JavaScript code. For example, you can
throw these errors in a callback when handling an error in a server-side response.
Calling Component Methods
Use <aura:method> to define a method as part of a component's API. This enables you to directly call a method in a component’s
client-side controller instead of firing and handling a component event. Using <aura:method> simplifies the code needed for
a parent component to call a method on a child component that it contains.
Using JavaScript Promises
You can use ES6 Promises in JavaScript code. Promises can simplify code that handles the success or failure of asynchronous calls,
or code that chains together multiple asynchronous calls.
Making API Calls
You can make API calls from client-side code, but it's not a best practice. Make API calls from server-side controllers instead to
maximize performance.

SEE ALSO:
Handling Events with Client-Side Controllers

Invoking Actions on Component Initialization

Use the init event to initialize a component or fire an event after component construction but before rendering.

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Component source
<aura:component>
<aura:attribute name="setMeOnInit" type="String" default="default value" />
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

<p>This value is set in the controller after the component initializes and before
rendering.</p>
<p><b>{!v.setMeOnInit}</b></p>

</aura:component>

Client-side controller source

({
doInit: function(cmp) {
// Set the attribute value.
// You could also fire an event here instead.
cmp.set("v.setMeOnInit", "controller init magic!");
}
})

Let's look at the Component source to see how this works. The magic happens in this line.
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

This registers an init event handler for the component. init is a predefined event sent to every component. After the component
is initialized, the doInit action is called in the component's controller. In this sample, the controller action sets an attribute value, but
it could do something more interesting, such as firing an event.

Note: You should never fire an event in a renderer so using the init event is a good alternative for many scenarios.

Setting value="{!this}" marks this as a value event. You should always use this setting for an init event.

SEE ALSO:
Handling Events with Client-Side Controllers
Create a Custom Renderer
Component Attributes
Detecting Data Changes with Change Handlers

Sharing JavaScript Code in a Component Bundle

Put functions that you want to reuse in the component’s helper. Helper functions also enable specialization of tasks, such as processing
data and firing server-side actions.
A helper function can be called from any JavaScript code in a component’s bundle, such as from a client-side controller or renderer.
Helper functions are similar to client-side controller functions in shape, surrounded by parentheses and curly braces to denote a JavaScript
object in object-literal notation containing a map of name-value pairs. A helper function can pass in any arguments required by the
function, such as the component it belongs to, a callback, or any other objects.
({
helperMethod1 : function() {
// logic here

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},

helperMethod2 : function(component) {
// logic here
this.helperMethod3(var1, var2);
},

helperMethod3 : function(var1, var2) {

// do something with var1 and var2 here
}
})

Creating a Helper
A helper file is part of the component bundle and is auto-wired via the naming convention, <componentName>Helper.js.

Note: If you want to call the same methods from multiple components, put the shared methods in a JavaScript library. A helper
allows you to only share methods within one component bundle.

Using a Helper in a Controller

Add a helper argument to a controller function to enable the function to use the helper. Specify (component, event,
helper) in the controller. These are standard parameters and you don't have to access them in the function. You can also pass in an
instance variable as a parameter, for example, createExpense: function(component, expense){...}, where
expense is a variable defined in the component.
The following code shows you how to call the updateItem helper function in a controller, which can be used with a custom event
handler.
/* controller */
({
newItemEvent: function(component, event, helper) {
helper.updateItem(component, event.getParam("item"));
}
})

Helper functions are local to a component, improve code reuse, and move the heavy lifting of JavaScript logic away from the client-side
controller where possible. The following code shows the helper function, which takes in the value parameter set in the controller via
the item argument. The code walks through calling a server-side action and returning a callback but you can do something else in
the helper function.
/* helper */
({
updateItem : function(component, item, callback) {
//Update the items via a server-side action
var action = component.get("c.saveItem");
action.setParams({"item" : item});
//Set any optional callback and enqueue the action
if (callback) {
action.setCallback(this, callback);
}
$A.enqueueAction(action);

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}
})

Using a Helper in a Renderer

Add a helper argument to a renderer function to enable the function to use the helper. In the renderer, specify (component,
helper) as parameters in a function signature to enable the function to access the component's helper. These are standard parameters
and you don't have to access them in the function. The following code shows an example on how you can override the afterRender()
function in the renderer and call open in the helper method.
detailsRenderer.js
({
afterRender : function(component, helper){
helper.open(component, null, "new");
}
})

detailsHelper.js
({
open : function(component, note, mode, sort){
if(mode === "new") {
//do something
}
// do something else, such as firing an event
}
})

SEE ALSO:
Create a Custom Renderer
Component Bundles
Handling Events with Client-Side Controllers

Using External JavaScript Libraries

To use an external JavaScript library in your apps, include a <script> tag in your .app file or include it in your app’s template.

SEE ALSO:
Creating App Templates
aura:application

Creating Reusable JavaScript Libraries

An Aura JavaScript library enables you to create a set of JavaScript files that can be used by any component that imports the library.

Creating a Library
Every library lives in a namespace and follows a naming convention. The c:myLib library points to a library in c/myLib/myLib.lib.

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A library is defined in a .lib file that starts with the <aura:library> tag. A library includes an arbitrary number of JavaScript
files. Each file is defined with an <aura:include> tag.
For example, this myLib.lib library includes three files.
<aura:library description="A set of global services">
<aura:include name="ViewService" />
<aura:include name="ErrorService" />
<aura:include name="LogService" imports="ErrorService"/>
</aura:library>

The name attribute of <aura:include> is the name of the JavaScript file with or without the .js suffix. For example,
name="ViewService" or name="ViewService.js" points to c/myLib/ViewService.js.

Note: The name attribute can only contain letters, numbers, dot, dash, and underscore characters and must start with a letter
or underscore.
The imports attribute of <aura:include> specifies another JavaScript file that is referenced and imported in the included file.
For example, this import specifies that LogService.js uses code in ErrorService.js.
<aura:include name="LogService" imports="ErrorService"/>

This example imports an OtherErrorService file that is used in a different library, othernamespace:otherLibrary.
<aura:include name="LogService"
imports="othernamespace:otherLibrary:OtherErrorService"/>

Use a comma-separated list to import more than one JavaScript file. This example imports multiple files.
<aura:include name="LogService" imports="ErrorService,BaseLogService"/>

Importing a Library
Use the <aura:import> tag in a component’s markup to import a library and enable usage of the library in the component’s
JavaScript files.
This markup imports the c:myLib library.
<aura:import library="c:myLib" property="BaseServices" />

The property attribute of <aura:import> is the variable name that can be used in the component’s helper to reference the
library.

Using a Library
You can reference the library in the helper of the component that imports the library by using the property attribute.
To reference one of the JavaScript files from the library in the helper, use this syntax:
var includedFile = this.<property>.<name>;

where <property> is defined by the <aura:import> tag, and <name> is defined by the <aura:include> tag. For
example:
var ViewService = this.BaseServices.ViewService;

BaseServices is the property value defined in the <aura:import> tag.

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To reference a library file in the controller, use this syntax:

var ViewService = helper.BaseServices.ViewService;

Format of Library Files

This type of library is for libraries stored locally on your filesystem. For external JavaScript libraries, see Using External JavaScript Libraries
instead.
Each file in a library must be a function and use a module pattern. The return value of the function is the singleton instance that is bound
to the helper of a component that imports the library.
For example, let’s look at a sample ViewService.js file that imports the ErrorService.js and BaseLogService.js
files.
<aura:include name="LogService" imports="ErrorService,BaseLogService" />

Here is ViewService.js:
function(ErrorService, BaseLogService) {
return {
getView: function() {
...
}
}
}

Note how the imported ErrorService.js and BaseLogService.js files are set as parameters in the opening function.
if you want to name the function parameters differently, you can configure aliases. For example:
<aura:include name="LogService" imports="ErrorService,BaseLogService"
aliases="es,bls" />

Here is ViewService.js using the aliases:

function(es, bls) {
return {
getView: function() {
...
}
}
}

The aliases are variables available in the lexical scope of the module and correspond one-to-one to the list of imports.
You can call the getView() function in a helper using this syntax:
var view = this.BaseServices.ViewService.getView();

Shim for Library Files

What if you have a library file that doesn't match the required format where each file must be a function? The framework can create a
shim to wrap a file in the required format. The shim enables you to use third-party code without having to modify it, which makes
maintenance and upgrades easier.

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For example, if you have a local copy of the Backbone library, you can create a file to manually wrap the code.
function($, _) {
// Original backbone code
return Backbone;
}

A better approach is to let the framework create the shim to wrap it in the required format.
<aura:include name="Backbone" imports="jQuery, Underscore"
aliases="$, _" export="Backbone"/>

The export attribute corresponds to the variable that exists in the lexical scope that you use in your helper.

Working with Attribute Values in JavaScript

These are useful and common patterns for working with attribute values in JavaScript.
component.get(String key) and component.set(String key, Object value) retrieves and assigns values
associated with the specified key on the component. Keys are passed in as an expression, which represents attribute values. To retrieve
an attribute value of a component reference, use component.find("cmpId").get("v.value"). Similarly, use
component.find("cmpId").set("v.value", myValue) to set the attribute value of a component reference. This
example shows how you can retrieve and set attribute values on a component reference, represented by the button with an ID of
button1.

<aura:component>
<aura:attribute name="buttonLabel" type="String"/>
<lightning:button aura:id="button1" label="Button 1"/>
{!v.buttonLabel}
<lightning:button label="Get Label" onclick="{!c.getLabel}"/>
</aura:component>

This controller action retrieves the label attribute value of a button in a component and sets its value on the buttonLabel
attribute.
({
getLabel : function(component, event, helper) {
var myLabel = component.find("button1").get("v.label");
component.set("v.buttonLabel", myLabel);
}
})

In the following examples, cmp is a reference to a component in your JavaScript code.

Get an Attribute Value

To get the value of a component’s label attribute:
var label = cmp.get("v.label");

Set an Attribute Value

To set the value of a component’s label attribute:
cmp.set("v.label","This is a label");

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Validate that an Attribute Value is Defined

To determine if a component’s label attribute is defined:
var isDefined = !$A.util.isUndefined(cmp.get("v.label"));

Validate that an Attribute Value is Empty

To determine if a component’s label attribute is empty:
var isEmpty = $A.util.isEmpty(cmp.get("v.label"));

SEE ALSO:
Accessing Models in JavaScript
Working with a Component Body in JavaScript

Working with a Component Body in JavaScript

These are useful and common patterns for working with a component’s body in JavaScript.
In these examples, cmp is a reference to a component in your JavaScript code. It’s usually easy to get a reference to a component in
JavaScript code. Remember that the body attribute is an array of components, so you can use the JavaScript Array methods on it.

Note: When you use cmp.set("v.body", ...) to set the component body, you must explicitly include {!v.body}
in your component markup.

Replace a Component's Body

To replace the current value of a component’s body with another component:
// newCmp is a reference to another component
cmp.set("v.body", newCmp);

Clear a Component's Body

To clear or empty the current value of a component’s body:
cmp.set("v.body", []);

Append a Component to a Component's Body

To append a newCmp component to a component’s body:
var body = cmp.get("v.body");
// newCmp is a reference to another component
body.push(newCmp);
cmp.set("v.body", body);

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Prepend a Component to a Component's Body

To prepend a newCmp component to a component’s body:
var body = cmp.get("v.body");
body.unshift(newCmp);
cmp.set("v.body", body);

Remove a Component from a Component's Body

To remove an indexed entry from a component’s body:
var body = cmp.get("v.body");
// Index (3) is zero-based so remove the fourth component in the body
body.splice(3, 1);
cmp.set("v.body", body);

SEE ALSO:
Component Body
Working with Attribute Values in JavaScript

Working with Events in JavaScript

These are useful and common patterns for working with events in JavaScript.
Events communicate data across components. Events can contain attributes with values set before the event is fired and read when the
event is handled.

Fire an Event
Fire a component event or an application event that’s registered on a component.
//Fire a component event
var compEvent = cmp.getEvent("sampleComponentEvent");
compEvent.fire();

//Fire an application event

var appEvent = $A.get("e.c:appEvent");
appEvent.fire();

For more information, see:

• Fire Component Events
• Fire Application Events

Get an Event Name

To get the name of the event that’s fired:
event.getSource().getName();

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Get an Event Parameter

To get an attribute that’s passed into an event:
event.getParam("value");

Get Parameters on an Event

To get all attributes that are passed into an event:
event.getParams();

event.getParams() returns an object containing all event parameters.

Get the Current Phase of an Event

To get the current phase of an event:
event.getPhase();

If the event hasn’t been fired, event.getPhase() returns undefined. Possible return values for component and application
events are capture, bubble, and default. Value events return default. For more information, see:
• Component Event Propagation
• Application Event Propagation

Get the Source Component

To get the component that fired the event:
event.getSource();

To retrieve an attribute on the component that fired the event:

event.getSource().get("v.myName");

Pause the Event

To pause the fired event:
event.pause();

If paused, the event is not handled until event.resume() is called. You can pause an event in the capture or bubble phase
only. For more information, see:
• Handling Bubbled or Captured Component Events
• Handling Bubbled or Captured Application Events

Prevent the Default Event Execution

To cancel the default action on the event:
event.preventDefault();

For example, you can prevent a lightning:button component from submitting a form when it’s clicked.

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Resume a Paused Event

To resume event handling for a paused event:
event.resume();

You can resume a paused event in the capture or bubble phase only. For more information, see:
• Handling Bubbled or Captured Component Events
• Handling Bubbled or Captured Application Events

Set a Value for an Event Parameter

To set a value for an event parameter:
event.setParam("name", cmp.get("v.myName");

If the event has already been fired, setting a parameter value has no effect on the event.

Set Values for Event Parameters

To set values for parameters on an event:
event.setParams({
key : value
});

If the event has already been fired, setting the parameter values has no effect on the event.

Stop Event Propagation

To prevent further propagation of an event:
event.stopPropagation();

You can stop event propagation in the capture or bubble phase only.

Modifying the DOM

The Document Object Model (DOM) is the language-independent model for representing and interacting with objects in HTML and
XML documents. It’s important to know how to modify the DOM safely so that the framework’s rendering service doesn’t stomp on your
changes and give you unexpected results.

IN THIS SECTION:
Modifying DOM Elements Managed by Aura
The framework creates and manages the DOM elements owned by a component. If you want to modify these DOM elements created
by the framework, modify the DOM elements in the handler for the component’s render event or in a custom renderer. Otherwise,
the framework will override your changes when the component is rerendered.
Modifying DOM Elements Managed by External Libraries
You can use different libraries, such as a charting library, to create and manage DOM elements. You don’t have to modify these DOM
elements within the render event handler or a renderer because they are managed by the external library.

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Modifying DOM Elements Managed by Aura

The framework creates and manages the DOM elements owned by a component. If you want to modify these DOM elements created
by the framework, modify the DOM elements in the handler for the component’s render event or in a custom renderer. Otherwise,
the framework will override your changes when the component is rerendered.
For example, if you modify DOM elements directly from a client-side controller, the changes may be overwritten when the component
is rendered.
You can read from the DOM outside a render event handler or a custom renderer.
The simplest approach is to leave DOM updates to the framework. Update a component’s attribute and use an expression in the markup.
The framework’s rendering service takes care of the DOM updates.
You can modify CSS classes for a component outside a renderer by using the $A.util.addClass(), $A.util.removeClass(),
and $A.util.toggleClass() methods.
There are some use cases where you want to perform post-processing on the DOM or react to rendering or rerendering of a component.
For these use cases, there are a few options.

IN THIS SECTION:
Handle the render Event
When a component is rendered or rerendered, the aura:valueRender event, also known as the render event, is fired.
Handle this event to perform post-processing on the DOM or react to component rendering or rerendering. The event is preferred
and easier to use than the alternative of creating a custom renderer.
Create a Custom Renderer
The framework’s rendering service takes in-memory component state and creates and manages the DOM elements owned by the
component. If you want to modify DOM elements created by the framework for a component, you can modify the DOM elements
in the component’s renderer. Otherwise, the framework will override your changes when the component is rerendered.

SEE ALSO:
Modifying DOM Elements Managed by External Libraries
Using Expressions
Dynamically Showing or Hiding Markup

Handle the render Event

When a component is rendered or rerendered, the aura:valueRender event, also known as the render event, is fired. Handle
this event to perform post-processing on the DOM or react to component rendering or rerendering. The event is preferred and easier
to use than the alternative of creating a custom renderer.
The render event is fired after all methods in a custom renderer are invoked. For more details on the sequence in the rendering or
rerendering lifecycles, see Create a Custom Renderer.
Handling the aura:valueRender event is similar to handling the init hook. Add a handler to your component's markup.
<aura:handler name="render" value="{!this}" action="{!c.onRender}"/>

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In this example, the onRender action in your client-side controller handles initial rendering and rerendering of the component. You
can choose any name for the action attribute.

SEE ALSO:
Invoking Actions on Component Initialization
Create a Custom Renderer

Create a Custom Renderer

The framework’s rendering service takes in-memory component state and creates and manages the DOM elements owned by the
component. If you want to modify DOM elements created by the framework for a component, you can modify the DOM elements in
the component’s renderer. Otherwise, the framework will override your changes when the component is rerendered.
The DOM is the language-independent model for representing and interacting with objects in HTML and XML documents. The framework
automatically renders your components so you don’t have to know anything more about rendering unless you need to customize the
default rendering behavior for a component.

Note: It’s preferred and easier to handle the render event rather than the alternative of creating a custom renderer.

Base Component Rendering

The base component in the framework is aura:component. Every component extends this base component.
The renderer for aura:component is in componentRenderer.js. This renderer has base implementations for the four phases
of the rendering and rerendering cycles:
• render()
• rerender()
• afterRender()
• unrender()
The framework calls these functions as part of the rendering and rerendering lifecycles and we will learn more about them soon. You
can override the base rendering functions in a custom renderer.

Rendering Lifecycle
The rendering lifecycle happens once in the lifetime of a component unless the component gets explicitly unrendered. When you create
a component:
1. The framework fires an init event, enabling you to update a component or fire an event after component construction but before
rendering.
2. The render() method is called to render the component’s body.
3. The afterRender() method is called to enable you to interact with the DOM tree after the framework’s rendering service has
inserted DOM elements.
4. The framework fires a render event, enabling you to interact with the DOM tree after the framework’s rendering service has
inserted DOM elements. Handling the render event is preferred to creating a custom renderer and overriding afterRender().

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Rerendering Lifecycle
The rerendering lifecycle automatically handles rerendering of components whenever the underlying data changes. Here is a typical
sequence.
1. A browser event triggers one or more Aura events.
2. Each Aura event triggers one or more actions that can update data. The updated data can fire more events.
3. The rendering service tracks the stack of events that are fired.
4. The framework rerenders all the components that own modified data by calling each component’s rerender() method.
5. The framework fires a render event, enabling you to interact with the DOM tree after the framework rerenders a component.
Handling the render event is preferred to creating a custom renderer and overriding rerender().
The component rerendering lifecycle repeats whenever the underlying data changes as long as the component is valid and not explicitly
unrendered.
For more information, see Events Fired During the Rendering Lifecycle .

Custom Renderer
You don’t normally have to write a custom renderer, but it’s useful when you want to interact with the DOM tree after the framework’s
rendering service has inserted DOM elements. If you want to customize rendering behavior and you can’t do it in markup or by using
the init event, you can create a client-side renderer.
A renderer file is part of the component bundle and is auto-wired if you follow the naming convention,
<componentName>Renderer.js. For example, the renderer for sample.cmp would be in sampleRenderer.js.
To reuse a renderer from another component, you can use the renderer system attribute in aura:component instead. For
example, this component uses the auto-wired renderer for docsample.sampleComponent in
docsample/sampleComponent/sampleComponentRenderer.js.

<aura:component
renderer="js://docsample.sampleComponent">
...
</aura:component>

Note: If you are reusing a renderer from another component and you already have an auto-wired renderer in your component
bundle, the methods in your auto-wired renderer will not be accessible. We recommend that you use a renderer within the
component bundle for maintainability and use an external renderer only if you must.

Note: These guidelines are important when you customize rendering.

• Only modify DOM elements that are part of the component. Never break component encapsulation by reaching in to another
component and changing its DOM elements, even if you are reaching in from the parent component.
• Never fire an event as it can trigger new rendering cycles. An alternative is to use an init event instead.
• Don’t set attribute values on other components as these changes can trigger new rendering cycles.
• Move as much of the UI concerns, including positioning, to CSS.

Customize Component Rendering

Customize rendering by creating a render() function in your component’s renderer to override the base render() function,
which updates the DOM.
The render() function returns a DOM node, an array of DOM nodes, or nothing. The base HTML component expects DOM nodes
when it renders a component.

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You generally want to extend default rendering by calling superRender() from your render() function before you add your
custom rendering code. Calling superRender() creates the DOM nodes specified in the markup.
This code outlines a custom render() function.
render : function(cmp, helper) {
var ret = this.superRender();
// do custom rendering here
return ret;
},

Rerender Components
When an event is fired, it may trigger actions to change data and call rerender() on affected components. The rerender()
function enables components to update themselves based on updates to other components since they were last rendered. This function
doesn’t return a value.
If you update data in a component, the framework automatically calls rerender().
You generally want to extend default rerendering by calling superRerender() from your renderer() function before you
add your custom rerendering code. Calling superRerender() chains the rerendering to the components in the body attribute.
This code outlines a custom rerender() function.
rerender : function(cmp, helper){
this.superRerender();
// do custom rerendering here
}

Access the DOM After Rendering

The afterRender() function enables you to interact with the DOM tree after the framework’s rendering service has inserted DOM
elements. It’s not necessarily the final call in the rendering lifecycle; it’s simply called after render() and it doesn’t return a value.
You generally want to extend default after rendering by calling superAfterRender() function before you add your custom code.
This code outlines a custom afterRender() function.
afterRender: function (component, helper) {
this.superAfterRender();
// interact with the DOM here
},

Unrender Components
The base unrender() function deletes all the DOM nodes rendered by a component’s render() function. It is called by the
framework when a component is being destroyed. Customize this behavior by overriding unrender() in your component’s renderer.
This method can be useful when you are working with third-party libraries that are not native to the framework.
You generally want to extend default unrendering by calling superUnrender() from your unrender() function before you
add your custom code.
This code outlines a custom unrender() function.
unrender: function () {
this.superUnrender();

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// do custom unrendering here

}

Ensure Client-Side Rendering

The framework calls the default server-side renderer by default, or a client-side renderer if you have one. To ensure client-side rendering
of a top-level component, append render="client" to the aura:component tag. Setting render="client" in the
top-level component takes precedence over the framework’s detection logic, which takes dependencies into consideration. This behavior
is useful if you’re testing the component in your browser and want to inspect the component using the client-side framework when
the test loads. Setting render="client" for test components ensures that the client-side framework is loaded, even though it
normally would’'t be needed.

SEE ALSO:
Modifying the DOM
Invoking Actions on Component Initialization
Component Bundles
Modifying Components Outside the Framework Lifecycle
Sharing JavaScript Code in a Component Bundle
Server-Side Rendering to the DOM

Modifying DOM Elements Managed by External Libraries

You can use different libraries, such as a charting library, to create and manage DOM elements. You don’t have to modify these DOM
elements within the render event handler or a renderer because they are managed by the external library.
A render event handler or a renderer are used only to customize DOM elements created and managed by Aura.

SEE ALSO:
Modifying DOM Elements Managed by Aura

Client-Side Runtime Binding of Components

A provider enables you to use an abstract component in markup. The framework uses the provider to determine the concrete component
to use at runtime.
Server-side providers are more common, but if you don't need to access the server when you're creating a component, you can use a
client-side provider instead.

Note: The framework behavior is undefined if a component has a client-side provider and a server-side provider that return
different values. It's preferable to only use a server-side or a client-side provider unless you need both.

Creating a Provider
A client-side provider is part of the component bundle and is auto-wired if you follow the naming convention,
<componentName>Provider.js.

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To reuse a provider from another component, you can use the provider system attribute in aura:component instead. For
example, this component uses the auto-wired provider for auradocs.sampleComponent in
auradocs/sampleComponent/sampleComponentProvider.js.

<aura:component
provider="js://auradocs.sampleComponent">
...
</aura:component>

Note: If you are reusing a provider from another component and you already have an auto-wired provider in your component
bundle, the methods in your auto-wired provider will not be accessible. We recommend that you use a provider within the
component bundle for maintainability and use an external provider only if you must.
A client-side provider is a simple JavaScript object that defines the provide function. For example, this provider returns a string that
defines the topic to display.
({
provide : function (cmp) {
var topic = cmp.get('v.topic');
return 'auradocs' + topic + 'Topic';
}
})

Instead of a string, a provider can return a JSON object to provide both the concrete component and set some additional attributes. For
example:
({
provide : function (cmp) {
var topic = cmp.get('v.topic');
return {
componentDef: 'auradocs' + topic + 'Topic',
attributes: {
"type": "task"
}
}
}
})

You can omit the componentDef entry if the component is already concrete and you only want to provide attributes.

Declaring Provider Dependencies

The framework automatically tracks dependencies between definitions, such as components. However, if a component uses a provider
that instantiates components that are not directly referenced elsewhere, use <aura:dependency> in the component markup to
explicitly tell the framework about the dependency, which wouldn't otherwise be discovered.

SEE ALSO:
Server-Side Runtime Binding of Components
Abstract Components
Interfaces
Component Bundles
aura:dependency

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Checking Component Validity

If you navigate elsewhere in the UI while asynchronous code is executing, the framework unrenders and destroys the component that
made the asynchronous request. You can still have a reference to that component, but it is no longer valid. The cmp.isValid()
call returns false for an invalid component.
If you call cmp.get() on an invalid component, cmp.get() returns null.
If you call cmp.set() on an invalid component, nothing happens and no error occurs. It’s essentially a no op.
In many scenarios, the cmp.isValid() call isn’t necessary because a null check on a value retrieved from cmp.get() is
sufficient. The main reason to call cmp.isValid() is if you’re making multiple calls against the component and you want to avoid
a null check for each result.

Inside the Framework Lifecycle

You don’t need a cmp.isValid() check in the callback in a client-side controller when you reference the component associated
with the client-side controller. The framework automatically checks that the component is valid. Similarly, you don’t need a
cmp.isValid() check during event handling or in a framework lifecycle hook, such as the init event.
Let’s look at a sample client-side controller.
({
"doSomething" : function(cmp) {
var action = cmp.get("c.serverEcho");
action.setCallback(this, function(response) {
var state = response.getState();
if (state === "SUCCESS") {
if (cmp.get("v.displayResult)) {
alert("From server: " + response.getReturnValue());
}
}
// other state handling omitted for brevity
});

$A.enqueueAction(action);
}
})

The component wired to the client-side controller is passed into the doSomething action as the cmp parameter. When
cmp.get("v.displayResult) is called, we don’t need a cmp.isValid() check.
However, if you hold a reference to another component that may not be valid despite your component being valid, you might need a
cmp.isValid() check for the other component. Let’s look at another example of a component that has a reference to another
component with a local ID of child.
({
"doSomething" : function(cmp) {
var action = cmp.get("c.serverEcho");
var child = cmp.find("child");
action.setCallback(this, function(response) {
var state = response.getState();
if (state === "SUCCESS") {
if (child.get("v.displayResult)) {
alert("From server: " + response.getReturnValue());
}

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}
// other state handling omitted for brevity
});

$A.enqueueAction(action);
}
})

This line in the previous example without the child component:

if (cmp.get("v.displayResult)) {

changed to:
if (child.get("v.displayResult)) {

You don’t need a child.isValid() call here as child.get("v.displayResult) will return null if the child component
is invalid. Add a child.isValid() check only if you’re making multiple calls against the child component and you want to avoid
a null check for each result.

Outside the Framework Lifecycle

If you reference a component in asynchronous code, such as setTimeout() or setInterval(), or when you use Promises, a
cmp.isValid() call checks that the component is still valid before processing the results of the asynchronous request. In many
scenarios, the cmp.isValid() call isn’t necessary because a null check on a value retrieved from cmp.get() is sufficient.
The main reason to call cmp.isValid() is if you’re making multiple calls against the component and you want to avoid a null
check for each result.
For example, you don’t need a cmp.isValid() check within this setTimeout() call as the cmp.set() call doesn’t do
anything when the component is invalid.
window.setTimeout(
$A.getCallback(function() {
cmp.set("v.visible", true);
}), 5000
);

SEE ALSO:
Handling Events with Client-Side Controllers
Invoking Actions on Component Initialization
Modifying Components Outside the Framework Lifecycle

Modifying Components Outside the Framework Lifecycle

Use $A.getCallback() to wrap any code that modifies a component outside the normal rerendering lifecycle, such as in a
setTimeout() call. The $A.getCallback() call ensures that the framework rerenders the modified component and processes
any enqueued actions.

Note: $A.run() is deprecated. Use $A.getCallback() instead.

You don't need to use $A.getCallback() if your code is executed as part of the framework's call stack; for example, your code is
handling an event or in the callback for a server-side controller action.

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An example of where you need to use $A.getCallback() is calling window.setTimeout() in an event handler to execute
some logic after a time delay. This puts your code outside the framework's call stack.
This sample sets the visible attribute on a component to true after a five-second delay.
window.setTimeout(
$A.getCallback(function() {
cmp.set("v.visible", true);
}), 5000
);

Note how the code updating a component attribute is wrapped in $A.getCallback(), which ensures that the framework rerenders
the modified component.

Note: You don't need a cmp.isValid() check within this setTimeout() call as the cmp.set() call doesn't do
anything when the component is invalid.

Warning: Don't save a reference to a function wrapped in $A.getCallback(). If you use the reference later to send actions,
the saved transaction state will cause the actions to be aborted.

SEE ALSO:
Handling Events with Client-Side Controllers
Checking Component Validity
Firing Aura Events from Non-Aura Code
Communicating with Events

Validating Fields
Validate user input, handle errors, and display error messages on input fields.
Client-side input validation is available for the following components:
• lightning:input
• lightning:select
• lightning:textarea
• ui:input*
Components in the lightning namespace simplify input validation by providing attributes to define error conditions, enabling you
to handle errors by checking the component’s validity state. For example, you can set a minimum length for a field , display an error
message when the condition is not met, and handle the error based on the given validity state.
Alternatively, input components in the ui namespace let you define and handle errors in a client-side controller, enabling you to iterate
through a list of errors.
The following sections discuss error handling for ui:input* components.

Default Error Handling

The framework can handle and display errors using the default error component, ui:inputDefaultError. This component is
dynamically created when you set the errors using the inputCmp.set("v.errors",[{message:"my error

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message"}]) syntax. The following example shows how you can handle a validation error and display an error message. Here is the
markup.
<!--c:errorHandling-->
<aura:component>
Enter a number: <ui:inputNumber aura:id="inputCmp"/> <br/>
<lightning:button label="Submit" onclick="{!c.doAction}"/>
</aura:component>

Here is the client-side controller.

/*errorHandlingController.js*/
{
doAction : function(component) {
var inputCmp = component.find("inputCmp");
var value = inputCmp.get("v.value");

// Is input numeric?
if (isNaN(value)) {
// Set error
inputCmp.set("v.errors", [{message:"Input not a number: " + value}]);
} else {
// Clear error
inputCmp.set("v.errors", null);
}
}
}

When you enter a value and click Submit, doAction in the controller validates the input and displays an error message if the input
is not a number. Entering a valid input clears the error. Add error messages to the input component using the errors attribute.

Custom Error Handling

ui:input and its child components can handle errors using the onError and onClearErrors events, which are wired to
your custom error handlers defined in a controller. onError maps to a ui:validationError event, and onClearErrors
maps to ui:clearErrors.
The following example shows how you can handle a validation error using custom error handlers and display the error message using
the default error component. Here is the markup.
<!--c:errorHandlingCustom-->
<aura:component>
Enter a number: <ui:inputNumber aura:id="inputCmp" onError="{!c.handleError}"
onClearErrors="{!c.handleClearError}"/> <br/>
<ui:button label="Submit" press="{!c.doAction}"/>
</aura:component>

Here is the client-side controller.

/*errorHandlingCustomController.js*/
{
doAction : function(component, event) {
var inputCmp = component.find("inputCmp");
var value = inputCmp.get("v.value");

// is input numeric?

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if (isNaN(value)) {
inputCmp.set("v.errors", [{message:"Input not a number: " + value}]);
} else {
inputCmp.set("v.errors", null);
}
},

handleError: function(component, event){

/* do any custom error handling
* logic desired here */
// get v.errors, which is an Object[]
var errorsArr = event.getParam("errors");
for (var i = 0; i < errorsArr.length; i++) {
console.log("error " + i + ": " + JSON.stringify(errorsArr[i]));
}
},

handleClearError: function(component, event) {

/* do any custom error handling
* logic desired here */
}
}

When you enter a value and click Submit, doAction in the controller executes. However, instead of letting the framework handle
the errors, we define a custom error handler using the onError event in <ui:inputNumber>. If the validation fails, doAction
adds an error message using the errors attribute. This automatically fires the handleError custom error handler.
Similarly, you can customize clearing the errors by using the onClearErrors event. See the handleClearError handler in
the controller for an example.

SEE ALSO:
Handling Events with Client-Side Controllers
Component Events

Throwing and Handling Errors

The framework gives you flexibility in handling unrecoverable and recoverable app errors in JavaScript code. For example, you can throw
these errors in a callback when handling an error in a server-side response.

Unrecoverable Errors
Use throw new Error("error message here") for unrecoverable errors, such as an error that prevents your app from
starting successfully. The error message and a stack trace are displayed.

Note: $A.error() is deprecated. Throw the native JavaScript Error object instead by using throw new Error().

This example shows you the basics of throwing an unrecoverable error in a JavaScript controller.
<!--c:unrecoverableError-->
<aura:component>
<lightning:button label="throw error" onclick="{!c.throwError}"/>
</aura:component>

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Here is the client-side controller source.

/*unrecoverableErrorController.js*/
({
throwError : function(component, event){
throw new Error("I can’t go on. This is the end.");
}
})

Recoverable Errors
Throw an instance of $A.auraFriendlyError() for recoverable errors.
This example shows you the basics of throwing and handling an error in a JavaScript controller.
<!--c:recoverableError-->
<aura:component>
<aura:handler event="aura:systemError" action="{!c.showError}"/>

<ui:button label="throw error" press="{!c.throwError}"/>

<div aura:id="myError" class="isDisplayed message" >
<ui:outputText aura:id="message" value=""/>
<lightning:button label="OK" onclick="{!c.hideError}"/>
</div>
</aura:component>

Click throw error to call throwError in the client-side controller.

In this simple example, we display an error message using a ui:outputText component. Typically, you use a component, such as
ui:message or ui:panel, to tell the user about the problem. Another button labeled OK lets you dismiss the error.
Here is the client-side controller source.
/*recoverableErrorController.js*/
({
throwError : function(cmp, event){
// error is an instance of AuraFriendlyError
// argument sets the message property of AuraFriendlyError
var error = new $A.auraFriendlyError("This is a sample error.");
// set an optional error data object
error.data = {
"moreErrorData1": "more1",
"moreErrorData2": "more2",
};
throw error;
},

showError: function(cmp, event) {

// handle the error by displaying a message
var myErrorCmp = cmp.find('myError');
var messageCmp = cmp.find('message');

// get the error object from aura:systemError event

// This is the AuraFriendlyError object
var afe = event.getParam('auraError');
if (afe) {

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// message is the argument set in AuraFriendlyError

var message = afe.message;
$A.util.removeClass(myErrorCmp, "isDisplayed");
messageCmp.set("v.value", message
+ JSON.stringify(afe.data));
}
// aura:systemError event has been handled
event["handled"] = true;
},

hideError : function(cmp){
// hide the error message from view
var myErrorCmp = cmp.find('myError');
$A.util.addClass(myErrorCmp,"isDisplayed");
}

})

The throwError method throws an instance of $A.auraFriendlyError(), which triggers firing of the aura:systemError
event.
Set the error message in the message property of AuraFriendlyError, which corresponds to the first argument of
$A.auraFriendlyError(). Set an optional object with more context in the data property of AuraFriendlyError.
An aura:systemError event handler in the markup calls showError to handle the error.
Set event["handled"]=true in showError to indicate that you’re providing your own error handler for the
aura:systemError event.
Here is the CSS.
/*recoverableError.css*/
.THIS.isDisplayed {
display: none;
}

SEE ALSO:
Validating Fields

Calling Component Methods

Use <aura:method> to define a method as part of a component's API. This enables you to directly call a method in a component’s
client-side controller instead of firing and handling a component event. Using <aura:method> simplifies the code needed for a
parent component to call a method on a child component that it contains.

Communicate Between Components

Use aura:method to communicate down the containment hierarchy. For example, a parent component calls an aura:method
on a child component that it contains.
To communicate up the containment hierarchy, fire a component event in the child component and handle it in the parent component.

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Syntax
Use this syntax to call a method in JavaScript code.
cmp.sampleMethod(arg1, … argN);

cmp is a reference to the component.

sampleMethod is the name of the aura:method.
arg1, … argN is an optional comma-separated list of arguments passed to the method. Each argument corresponds to an
aura:attribute defined in the aura:method markup.

Using Inherited Methods

A sub component that extends a super component has access to any methods defined in the super component.
An interface can also include an <aura:method> tag. A component that implements the interface can access the method.

Example
Let's look at an example app.
<!-- c:auraMethodCallerWrapper.app -->
<aura:application >
<c:auraMethodCaller />
</aura:application>

c:auraMethodCallerWrapper.app contains a c:auraMethodCaller component.

<!-- c:auraMethodCaller.cmp -->

<aura:component >
<p>Parent component calls aura:method in child component</p>
<c:auraMethod aura:id="child" />

...
</aura:component>

c:auraMethodCaller is the parent component. c:auraMethodCaller contains the child component, c:auraMethod.
We'll show how c:auraMethodCaller calls an aura:method defined in c:auraMethod.
We'll use c:auraMethodCallerWrapper.app to see how to return results from synchronous and asynchronous code.

IN THIS SECTION:
Return Result for Synchronous Code
aura:method executes synchronously. A synchronous method finishes executing before it returns. Use the return statement
to return a value from synchronous JavaScript code.

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Return Result for Asynchronous Code

aura:method executes synchronously. Use the return statement to return a value from synchronous JavaScript code. JavaScript
code that calls a server-side action is asynchronous. Asynchronous code can continue to execute after it returns. You can’t use the
return statement to return the result of an asynchronous call because the aura:method returns before the asynchronous
code completes. For asynchronous code, use a callback instead of a return statement.

SEE ALSO:
aura:method
Component Events

Return Result for Synchronous Code

aura:method executes synchronously. A synchronous method finishes executing before it returns. Use the return statement to
return a value from synchronous JavaScript code.
An asynchronous method can continue to execute after it returns. JavaScript code often uses the callback pattern to return a result after
asynchronous code completes. We’ll describe later how to return a result for an asynchronous action.

Step 1: Define aura:method in Markup

Let’s look at a logParam aura:method that executes synchronous code. We’ll use the c:auraMethodCallerWrapper.app
and components outlined in Calling Component Methods. Here’s the markup that defines the aura:method.
<!-- c:auraMethod -->
<aura:component>
<aura:method name="logParam"
description="Sample method with parameter">
<aura:attribute name="message" type="String" default="default message" />
</aura:method>

<p>This component has an aura:method definition.</p>

</aura:component>

The logParam aura:method has an aura:attribute with a name of message. This attribute enables you to set a
message parameter when you call the logParam method.
The name attribute of logParam configures the aura:method to invoke logParam() in the client-side controller.
An aura:method can have multiple aura:attribute tags. Each aura:attribute corresponds to a parameter that you
can pass into the aura:method. For more details on the syntax, see aura:method.
You don’t explicitly declare a return value in the aura:method markup. You just use a return statement in the JavaScript controller.

Step 2: Implement aura:method Logic in Controller

The logParam aura:method invokes logParam() in auraMethodController.js. Let’s look at that source.
/* auraMethodController.js */
({
logParam : function(cmp, event) {
var params = event.getParam('arguments');
if (params) {
var message = params.message;

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console.log("message: " + message);

return message;
}
},
})

logParam() simply logs the parameter passed in and returns the parameter value to demonstrate how to use the return statement.
If your code is synchronous, you can use a return statement; for example, you’re not making an asynchronous server-side action call.

Step 3: Call aura:method from Parent Controller

callAuraMethod() in the controller for c:auraMethodCaller calls the logParam aura:method defined in its child
component, c:auraMethod. Here’s the controller for c:auraMethodCaller.
/* auraMethodCallerController.js */
({
callAuraMethod : function(component, event, helper) {
var childCmp = component.find("child");
// call the aura:method in the child component
var auraMethodResult =
childCmp.logParam("message sent by parent component");
console.log("auraMethodResult: " + auraMethodResult);
},
})

callAuraMethod() finds the child component, c:auraMethod, and calls its logParam aura:method with an argument
for the message parameter of the aura:method.
childCmp.logParam("message sent by parent component");

auraMethodResult is the value returned from logParam.

Step 4: Add Button to Initiate Call to aura:method

The c:auraMethodCaller markup contains a lightning:button that invokes callAuraMethod() in
auraMethodCallerController.js. We use this button to initiate the call to aura:method in the child component.

<!-- c:auraMethodCaller.cmp -->

<aura:component >
<p>Parent component calls aura:method in child component</p>
<c:auraMethod aura:id="child" />

<lightning:button label="Call aura:method in child component"

onclick="{! c.callAuraMethod}" />
</aura:component>

SEE ALSO:
Return Result for Asynchronous Code
Calling Component Methods
aura:method

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Return Result for Asynchronous Code

aura:method executes synchronously. Use the return statement to return a value from synchronous JavaScript code. JavaScript
code that calls a server-side action is asynchronous. Asynchronous code can continue to execute after it returns. You can’t use the
return statement to return the result of an asynchronous call because the aura:method returns before the asynchronous code
completes. For asynchronous code, use a callback instead of a return statement.

Step 1: Define aura:method in Markup

Let’s look at an echo aura:method that uses a callback. We’ll use the c:auraMethodCallerWrapper.app and components
outlined in Calling Component Methods. Here’s the echo aura:method in the c:auraMethod component.
<!-- c:auraMethod -->
<aura:component controller="SimpleServerSideController">
<aura:method name="echo"
description="Sample method with server-side call">
<aura:attribute name="callback" type="Function" />
</aura:method>

<p>This component has an aura:method definition.</p>

</aura:component>

The echo aura:method has an aura:attribute with a name of callback. This attribute enables you to set a callback that’s
invoked by the aura:method after execution of the server-side action in SimpleServerSideController.

Step 2: Implement aura:method Logic in Controller

The echo aura:method invokes echo() in auraMethodController.js. Let’s look at the source.
/* auraMethodController.js */
({
echo : function(cmp, event) {
var params = event.getParam('arguments');
var callback;
if (params) {
callback = params.callback;
}

var action = cmp.get("c.serverEcho");

action.setCallback(this, function(response) {
var state = response.getState();
if (state === "SUCCESS") {
console.log("From server: " + response.getReturnValue());
// return doesn't work for async server action call
//return response.getReturnValue();
// call the callback passed into aura:method
if (callback) callback(response.getReturnValue());
}
else if (state === "INCOMPLETE") {
// do something
}
else if (state === "ERROR") {
var errors = response.getError();
if (errors) {

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if (errors[0] && errors[0].message) {

console.log("Error message: " +
errors[0].message);
}
} else {
console.log("Unknown error");
}
}
});
$A.enqueueAction(action);
},
})

echo() calls the serverEcho() server-side controller action, which we’ll create next.

Note: You can’t return the result with a return statement. The aura:method returns before the asynchronous server-side
action call completes. Instead, we invoke the callback passed into the aura:method and set the result as a parameter in the
callback.

Step 3: Create Apex Server-Side Controller

The echo aura:method calls a server-side controller action called serverEcho. Here’s the source for the server-side controller.
public with sharing class SimpleServerSideController {
@AuraEnabled
public static String serverEcho() {
return ('Hello from the server');
}
}

The serverEcho() method returns a String.

Step 4: Call aura:method from Parent Controller

Here’s the controller for c:auraMethodCaller. It calls the echo aura:method in its child component, c:auraMethod.
/* auraMethodCallerController.js */
({
callAuraMethodServerTrip : function(component, event, helper) {
var childCmp = component.find("child");
// call the aura:method in the child component
childCmp.echo(function(result) {
console.log("callback for aura:method was executed");
console.log("result: " + result);
});
},
})

callAuraMethodServerTrip() finds the child component, c:auraMethod, and calls its echo aura:method. echo()
passes a callback function into the aura:method.
The callback configured in auraMethodCallerController.js logs the result.
function(result) {
console.log("callback for aura:method was executed");

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console.log("result: " + result);

}

Step 5: Add Button to Initiate Call to aura:method

The c:auraMethodCaller markup contains a lightning:button that invokes callAuraMethodServerTrip()
in auraMethodCallerController.js. We use this button to initiate the call to the aura:method in the child component.
Here’s the markup for c:auraMethodCaller.
<!-- c:auraMethodCaller.cmp -->
<aura:component >
<p>Parent component calls aura:method in child component</p>
<c:auraMethod aura:id="child" />

<lightning:button label="Call aura:method (server trip) in child component"

onclick="{! c.callAuraMethodServerTrip}" />
</aura:component>

SEE ALSO:
Return Result for Synchronous Code
Calling Component Methods
aura:method

Using JavaScript Promises

You can use ES6 Promises in JavaScript code. Promises can simplify code that handles the success or failure of asynchronous calls, or
code that chains together multiple asynchronous calls.
If the browser doesn’t provide a native version, the framework uses a polyfill so that promises work in all browsers supported for Lightning
Experience.
We assume that you are familiar with the fundamentals of promises. For a great introduction to promises, see
https://developers.google.com/web/fundamentals/getting-started/primers/promises.
Promises are an optional feature. Some people love them, some don’t. Use them if they make sense for your use case.

Create a Promise
This firstPromise function returns a Promise.
firstPromise : function() {
return new Promise($A.getCallback(function(resolve, reject) {
// do something

if (/* success */) {

resolve("Resolved");
}
else {
reject("Rejected");
}

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}));
}

The promise constructor determines the conditions for calling resolve() or reject() on the promise.

Chaining Promises
When you need to coordinate or chain together multiple callbacks, promises can be useful. The generic pattern is:
firstPromise()
.then(
// resolve handler
$A.getCallback(function(result) {
return anotherPromise();
}),

// reject handler
$A.getCallback(function(error) {
console.log("Promise was rejected: ", error);
return errorRecoveryPromise();
})
)
.then(
// resolve handler
$A.getCallback(function() {
return yetAnotherPromise();
})
);

The then() method chains multiple promises. In this example, each resolve handler returns another promise.
then() is part of the Promises API. It takes two arguments:
1. A callback for a fulfilled promise (resolve handler)
2. A callback for a rejected promise (reject handler)
The first callback, function(result), is called when resolve() is called in the promise constructor. The result object in
the callback is the object passed as the argument to resolve().
The second callback, function(error), is called when reject() is called in the promise constructor. The error object in
the callback is the object passed as the argument to reject().

Note: The two callbacks are wrapped by $A.getCallback() in our example. What’s that all about? Promises execute their
resolve and reject functions asynchronously so the code is outside the Aura event loop and normal rendering lifecycle. If the resolve
or reject code makes any calls to Aura, such as setting a component attribute, use $A.getCallback() to wrap the code. For
more information, see Modifying Components Outside the Framework Lifecycle on page 169.

Always Use catch() or a Reject Handler

The reject handler in the first then() method returns a promise with errorRecoveryPromise(). Reject handlers are often
used "midstream" in a promise chain to trigger an error recovery mechanism.
The Promises API includes a catch() method to optionally catch unhandled errors. Always include a reject handler or a catch()
method in your promise chain.

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Throwing an error in a promise doesn’t trigger window.onerror, which is where the framework configures its global error handler.
If you don't have a catch() method, keep an eye on your browser’s console during development for reports about uncaught errors
in a promise. To show an error message in a catch() method, use $A.reportError(). The syntax for catch() is:
promise.then(...)
.catch(function(error) {
$A.reportError("error message here", error);
});

For more information on catch(), see the Mozilla Developer Network.

Don’t Use Storable Actions in Promises

The framework stores the response for storable actions in client-side cache. This stored response can dramatically improve the performance
of your app and allow offline usage for devices that temporarily don’t have a network connection. Storable actions are only suitable for
read-only actions.
Storable actions might have their callbacks invoked more than once: first with cached data, then with updated data from the server. The
multiple invocations don't align well with promises, which are expected to resolve or reject only once.

Using Promises in Tests

You can return a promise from the current test stage and the test framework will wait for that promise to resolve or reject before
continuing to the next test stage or completing the test. You don’t need any boilerplate code to handle errors or wait for promises to
complete.
Here’s an example:
testThatUsesPromises: {
test: function(cmp) {
return somePromise()
.then(function() {
return anotherPromise();
});
}
}

SEE ALSO:
Storable Actions

Making API Calls

You can make API calls from client-side code, but it's not a best practice. Make API calls from server-side controllers instead to maximize
performance.
The framework uses an XMLHttpRequest (XHR) to communicate from the client to the server and server-side actions are designed
to minimize network traffic and provide a smoother user experience.
Batching of Actions
The framework queues up actions before sending them to the server. This mechanism is largely transparent to you when you’re
writing code but it enables the framework to minimize network traffic by batching multiple actions into one request (XHR). For more
information, see Queueing of Server-Side Actions on page 206.

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Abortable Actions
Mark an action as abortable to make it potentially abortable while it's queued to be sent to the server. An abortable action in the
queue is not sent to the server if the component that created the action is no longer valid, that is cmp.isValid() == false.
A component is automatically destroyed and marked invalid by the framework when it is unrendered. For more information, see
Abortable Actions on page 211.
Storable Actions
Enhance your component’s performance by marking actions as storable to quickly show cached data from client-side storage without
waiting for a server trip. If the cached data is stale, the framework retrieves the latest data from the server. Caching is especially
beneficial for users on high latency, slow, or unreliable connections such as 3G networks. For more information, see Storable Actions
on page 208.
Background Actions
An action can be marked as a background action. This is useful when you want your app to remain responsive to a user while it
executes a low priority, long-running action. A rough guideline is to use a background action if it takes more than five seconds for
the response to return from the server. For more information, see Foreground and Background Actions on page 206.

JavaScript Cookbook
This section includes code snippets and samples that can be used in various JavaScript files.

IN THIS SECTION:
Dynamically Creating Components
Create a component dynamically in your client-side JavaScript code by using the $A.createComponent() method. To create
multiple components, use $A.createComponents().
Detecting Data Changes with Change Handlers
Configure a component to automatically invoke a change handler, which is a client-side controller action, when a value in one of
the component's attributes changes.
Finding Components by ID
Retrieve a component by its ID in JavaScript code.
Dynamically Adding Event Handlers To a Component
You can dynamically add a handler for an event that a component fires.
Creating a Document-Level Event Handler
To create a document-level event handler, call addDocumentLevelHandler(String eventName, Function
callback, Boolean autoEnable). This creates and returns a handler object that can be enabled and disabled with
setEnabled(Boolean).
Dynamically Showing or Hiding Markup
You can use CSS to toggle markup visibility. However, <aura:if> is the preferred approach because it defers the creation and
rendering of the enclosed element tree until needed.
Adding and Removing Styles
You can add or remove a CSS style on a component or element during runtime.
Which Button Was Pressed?
To find out which button was pressed in a component containing multiple buttons, use Component.getLocalId().
Formatting Dates in JavaScript
The AuraLocalizationService JavaScript API provides methods for formatting and localizing dates.

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Dynamically Creating Components

Create a component dynamically in your client-side JavaScript code by using the $A.createComponent() method. To create
multiple components, use $A.createComponents().

Note: Use $A.createComponent() instead of the deprecated newComponent(), newComponentAsync(), and

newComponentDeprecated() methods of AuraComponentService or the deprecated newCmp() and
newCmpAsync() methods of $A.
The syntax is:
$A.createComponent(String type, Object attributes, function callback)

1. type—The type of component to create; for example, "ui:button".

2. attributes—A map of attributes for the component, including the local Id (aura:id) and flavor (aura:flavor).
3. callback(cmp, status, errorMessage)—The callback to invoke after the component is created. The callback has
three parameters.
a. cmp—The component that was created. This enables you to do something with the new component, such as add it to the
body of the component that creates it. If there’s an error, cmp is null.
b. status—The status of the call. The possible values are SUCCESS, INCOMPLETE, or ERROR. Always check that the status
is SUCCESS before you try to use the component.
c. errorMessage—The error message if the status is ERROR.

Let’s add a dynamically created button to this sample component.

<!--c:createComponent-->
<aura:component>
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

<p>Dynamically created button</p>

{!v.body}
</aura:component>

The client-side controller calls $A.createComponent() to create a ui:button with a local ID and a handler for the press
event. The function(newButton, ...) callback appends the button to the body of c:createComponent. The
newButton that’s dynamically created by $A.createComponent() is passed as the first argument to the callback.

/*createComponentController.js*/
({
doInit : function(cmp) {
$A.createComponent(
"lightning:button",
{
"aura:id": "findableAuraId",
"label": "Press Me",
"onclick": cmp.getReference("c.handlePress")
},
function(newButton, status, errorMessage){
//Add the new button to the body array
if (status === "SUCCESS") {
var body = cmp.get("v.body");
body.push(newButton);
cmp.set("v.body", body);

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}
else if (status === "INCOMPLETE") {
console.log("No response from server or client is offline.")
// Show offline error
}
else if (status === "ERROR") {
console.log("Error: " + errorMessage);
// Show error message
}
}
);
},

handlePress : function(cmp) {
console.log("button pressed");
}
})

Note: c:createComponent contains a {!v.body} expression. When you use cmp.set("v.body", ...) to set
the component body, you must explicitly include {!v.body} in your component markup.

Creating Nested Components

To dynamically create a component in the body of another component, use $A.createComponents() to create the components.
In the function callback, nest the components by setting the inner component in the body of the outer component. This example
creates a ui:outputText component in the body of a ui:message component.
$A.createComponents([
["ui:message",{
"title" : "Sample Thrown Error",
"severity" : "error",
}],
["ui:outputText",{
"value" : e.message
}]
],
function(components, status, errorMessage){
if (status === "SUCCESS") {
var message = components[0];
var outputText = components[1];
// set the body of the ui:message to be the ui:outputText
message.set("v.body", outputText);
}
else if (status === "INCOMPLETE") {
console.log("No response from server or client is offline.")
// Show offline error
}
else if (status === "ERROR") {
console.log("Error: " + errorMessage);
// Show error message
}
}
);

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Destroying Dynamically Created Components

After a component that is declared in markup is no longer in use, the framework automatically destroys it and frees up its memory.
If you create a component dynamically in JavaScript and that component isn't added to a facet (v.body or another attribute of type
Aura.Component[]), you have to destroy it manually using Component.destroy() to avoid memory leaks.

Avoiding a Server Trip

The createComponent() and createComponents() methods support both client-side and server-side component creation.
For performance and other reasons, client-side creation is preferred. If no server-side dependencies are found, the methods are executed
client-side. The top-level component determines whether a server request is necessary for component creation.
The framework automatically tracks dependencies between definitions, such as components, defined in markup. These dependencies
are loaded with the component. However, some dependencies aren’t easily discoverable by the framework; for example, if you dynamically
create a component that isn’t directly referenced in the component’s markup. To tell the framework about such a dynamic dependency,
use the <aura:dependency> tag. This declaration ensures that the component and its dependencies are sent to the client.
A component with server-side dependencies must be created on the server. Server-side dependencies include server-side models,
renderers, or providers for the component and its super components. Using any server-side models for the component and its super
components is a server-side dependency.

Note: A server-side controller isn’t a server-side dependency for component creation because controller actions are only called
after the component has been created.
A single call to createComponent() or createComponents() can result in many components being created. The call creates
the requested component and all its child components. In addition to performance considerations, server-side component creation has
a limit of 10,000 components that can be created in a single request. If you hit this limit, ensure you’re explicitly declaring component
dependencies with the <aura:dependency> tag or otherwise pre-loading dependent elements, so that your component can be
created on the client side instead.
There’s no limit on component creation on the client side.

Note: Creating components where the top-level components don’t have server dependencies but nested inner components do
isn’t currently supported.

SEE ALSO:
Reference Doc App
aura:dependency
Invoking Actions on Component Initialization
Dynamically Adding Event Handlers To a Component
Styling with Flavors

Detecting Data Changes with Change Handlers

Configure a component to automatically invoke a change handler, which is a client-side controller action, when a value in one of the
component's attributes changes.
When the value changes, the valueChange.evt event is automatically fired. The event has type="VALUE".
In the component, define a handler with name="change".
<aura:handler name="change" value="{!v.numItems}" action="{!c.itemsChange}"/>

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The value attribute sets the component attribute that the change handler tracks.
The action attribute sets the client-side controller action to invoke when the attribute value changes.
A component can have multiple <aura:handler name="change"> tags to detect changes to different attributes.
In the controller, define the action for the handler.
({
itemsChange: function(cmp, evt) {
console.log("numItems has changed");
console.log("old value: " + evt.getParam("oldValue"));
console.log("current value: " + evt.getParam("value"));
}
})

The valueChange event gives you access to the previous value (oldValue) and the current value (value) in the handler action.
When a change occurs to a value that is represented by the change handler, the framework handles the firing of the event and
rerendering of the component.

SEE ALSO:
Invoking Actions on Component Initialization
aura:valueChange

Finding Components by ID
Retrieve a component by its ID in JavaScript code.
Use aura:id to add a local ID of button1 to the lightning:button component.
<lightning:button aura:id="button1" label="button1"/>

You can find the component by calling cmp.find("button1"), where cmp is a reference to the component containing the
button. The find() function has one parameter, which is the local ID of a component within the markup.
find() returns different types depending on the result.
• If the local ID is unique, find() returns the component.
• If there are multiple components with the same local ID, find() returns an array of the components.
• If there is no matching local ID, find() returns undefined.

SEE ALSO:
Component IDs
Value Providers

Dynamically Adding Event Handlers To a Component

You can dynamically add a handler for an event that a component fires.
The addEventHandler() method in the Component object replaces the deprecated addHandler() method.
To add an event handler to a component dynamically, use the addEventHandler() method.
addEventHandler(String event, Function handler, String phase, String includeFacets)

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Creating Apps Dynamically Adding Event Handlers To a Component

event
The first argument is the name of the event that triggers the handler. You can’t force a component to start firing events that it doesn’t
fire, so make sure that this argument corresponds to an event that the component fires. The <aura:registerEvent> tag in
a component’s markup advertises an event that the component fires.
• For a component event, set this argument to match the name attribute of the <aura:registerEvent> tag.
• For an application event, set this argument to match the event descriptor in the format namespace:eventName.
handler
The second argument is the action that handles the event. The format is similar to the value you would put in the action attribute
in the <aura:handler> tag if the handler was statically defined in the markup. There are two options for this argument.
• To use a controller action, use the format: cmp.getReference("c.actionName").
• To use an anonymous function, use the format:
function(auraEvent) {
// handling logic here
}

For a description of the other arguments, see the JavaScript API in the doc reference app.
You can also add an event handler to a component that is created dynamically in the callback function of $A.createComponent().
For more information, see Dynamically Creating Components.

Example
This component has buttons to fire and handle a component event and an application event.
<!--c:dynamicHandler-->
<aura:component >
<aura:registerEvent name="compEvent" type="c:sampleEvent"/>
<aura:registerEvent name="appEvent" type="c:appEvent"/>
<h1>Add dynamic handler for event</h1>
<p>
<lightning:button label="Fire component event" onclick="{!c.fireEvent}" />
<lightning:button label="Add dynamic event handler for component event"
onclick="{!c.addEventHandler}" />
</p>
<p>
<lightning:button label="Fire application event" onclick="{!c.fireAppEvent}" />
<lightning:button label="Add dynamic event handler for application event"
onclick="{!c.addAppEventHandler}" />
</p>

</aura:component>

Here’s the client-side controller.

/* dynamicHandlerController.js */
({
fireEvent : function(cmp, event) {
// Get the component event by using the
// name value from <aura:registerEvent> tag
var compEvent = cmp.getEvent("compEvent");
compEvent.fire();

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console.log("Fired a component event");

},

addEventHandler : function(cmp, event) {

// First param matches name attribute in <aura:registerEvent> tag
cmp.addEventHandler("compEvent", cmp.getReference("c.handleEvent"));
console.log("Added handler for component event");
},

handleEvent : function(cmp, event) {

alert("Handled the component event");
},

fireAppEvent : function(cmp, event) {

var appEvent = $A.get("e.c:appEvent");
appEvent.fire();
console.log("Fired an application event");
},

addAppEventHandler : function(cmp, event) {

// Can use cmp.getReference() or anonymous function for handler
// First param is event descriptor, "c:appEvent", for application events
cmp.addEventHandler("c:appEvent", cmp.getReference("c.handleAppEvent"));
// Can alternatively use anonymous function for handler
//cmp.addEventHandler("c:appEvent", function(auraEvent) {
// console.log("Handled the application event in anonymous function");
//});
console.log("Added handler for application event");
},

handleAppEvent : function(cmp, event) {

alert("Handled the application event");
}
})

Notice the first parameter of the addEventHandler() calls. The syntax for a component event is:
cmp.addEventHandler("compEvent", cmp.getReference("c.handleEvent"));

The syntax for an application event is:

cmp.addEventHandler("c:appEvent", cmp.getReference("c.handleAppEvent"));

For either a component or application event, you can use an anonymous function as a handler instead of using cmp.getReference()
for a controller action.
For example, the application event handler could be:
cmp.addEventHandler("c:appEvent", function(auraEvent) {
// add handler logic here

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console.log("Handled the application event in anonymous function");

});

SEE ALSO:
Handling Events with Client-Side Controllers
Handling Component Events
Reference Doc App

Creating a Document-Level Event Handler

To create a document-level event handler, call addDocumentLevelHandler(String eventName, Function
callback, Boolean autoEnable). This creates and returns a handler object that can be enabled and disabled with
setEnabled(Boolean).

Note: Document-level event handlers are global objects so using many of them could have performance implications.

An example of when a document-level event handler can be useful is with modal dialogs that should close when someone clicks outside
of them. Here is an example of how to add a document-level event handler. This code is from the datePickerHelper.js code
that is part of the datePicker component:
updateGlobalEventListeners: function(component) {
var concreteCmp = component.getConcreteComponent();
var visible = concreteCmp.get("v.visible");
if (!concreteCmp._clickStart) {
concreteCmp._clickStart = concreteCmp.addDocumentLevelHandler(
this.getOnClickEventProp("onClickStartEvent"),
this.getOnClickStartFunction(component),
visible);
concreteCmp._clickEnd = concreteCmp.addDocumentLevelHandler(
this.getOnClickEventProp("onClickEndEvent"),
this.getOnClickEndFunction(component),
visible);
} else {
concreteCmp._clickStart.setEnabled(visible);
concreteCmp._clickEnd.setEnabled(visible);
}
},

The document-level event handlers will be cleaned up automatically when the component is destroyed. If you need to destroy the
document-level event handler earlier, call removeDocumentLevelHandler().

Dynamically Showing or Hiding Markup

You can use CSS to toggle markup visibility. However, <aura:if> is the preferred approach because it defers the creation and
rendering of the enclosed element tree until needed.
For an example using <aura:if>, see Best Practices for Conditional Markup.
This example uses $A.util.toggleClass(cmp, 'class') to toggle visibility of markup.
<!--c:toggleCss-->
<aura:component>

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<lightning:button label="Toggle" onclick="{!c.toggle}"/>

<p aura:id="text">Now you see me</p>
</aura:component>

/*toggleCssController.js*/
({
toggle : function(component, event, helper) {
var toggleText = component.find("text");
$A.util.toggleClass(toggleText, "toggle");
}
})

/*toggleCss.css*/
.THIS.toggle {
display: none;
}

Click the Toggle button to hide or show the text by toggling the CSS class.

SEE ALSO:
Handling Events with Client-Side Controllers
Component Attributes
Adding and Removing Styles

Adding and Removing Styles

You can add or remove a CSS style on a component or element during runtime.
To retrieve the class name on a component, use component.find('myCmp').get('v.class'), where myCmp is the
aura:id attribute value.
To append and remove CSS classes from a component or element, use the $A.util.addClass(cmpTarget, 'class')
and $A.util.removeClass(cmpTarget, 'class') methods.
Component source
<aura:component>
<div aura:id="changeIt">Change Me!</div><br />
<lightning:button onclick="{!c.applyCSS}" label="Add Style" />
<lightning:button onclick="{!c.removeCSS}" label="Remove Style" />
</aura:component>

CSS source
.THIS.changeMe {
background-color:yellow;
width:200px;
}

Client-side controller source

{
applyCSS: function(cmp, event) {
var cmpTarget = cmp.find('changeIt');
$A.util.addClass(cmpTarget, 'changeMe');

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Creating Apps Which Button Was Pressed?

},

removeCSS: function(cmp, event) {

var cmpTarget = cmp.find('changeIt');
$A.util.removeClass(cmpTarget, 'changeMe');
}
}

The buttons in this demo are wired to controller actions that append or remove the CSS styles. To append a CSS style to a component,
use $A.util.addClass(cmpTarget, 'class'). Similarly, remove the class by using
$A.util.removeClass(cmpTarget, 'class') in your controller. cmp.find() locates the component using the local
ID, denoted by aura:id="changeIt" in this demo.

Toggling a Class
To toggle a class, use $A.util.toggleClass(cmp, 'class'), which adds or removes the class.
The cmp parameter can be component or a DOM element.

Note: We recommend using a component instead of a DOM element. If the utility function is not used inside afterRender()
or rerender(), passing in cmp.getElement() might result in your class not being applied when the components are
rerendered. For more information, see Events Fired During the Rendering Lifecycle on page 127.
To hide or show markup dynamically, see Dynamically Showing or Hiding Markup on page 190.
To conditionally set a class for an array of components, pass in the array to $A.util.toggleClass().
mapClasses: function(arr, cssClass) {
for(var cmp in arr) {
$A.util.toggleClass(arr[cmp], cssClass);
}
}

SEE ALSO:
Handling Events with Client-Side Controllers
CSS in Components
Component Bundles

Which Button Was Pressed?

To find out which button was pressed in a component containing multiple buttons, use Component.getLocalId().
The framework provides two button components—ui:button and lightning:button.

Note: We recommend that you use lightning:button, a button component that comes with Lightning Design System
styling.
Let’s look at an example with multiple ui:button components. Each button has a unique local ID, set by an aura:id attribute.
<!--c:buttonPressed-->
<aura:component>
<aura:attribute name="whichButton" type="String" />

<p>You clicked: {!v.whichButton}</p>

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<ui:button aura:id="button1" label="Click me" press="{!c.nameThatButton}"/>

<ui:button aura:id="button2" label="Click me too" press="{!c.nameThatButton}"/>
</aura:component>

Use event.getSource() in the client-side controller to get the button component that was clicked. Call getLocalId() to
get the aura:id of the clicked button.
/* buttonPressedController.js */
({
nameThatButton : function(cmp, event, helper) {
var whichOne = event.getSource().getLocalId();
console.log(whichOne);
cmp.set("v.whichButton", whichOne);
}
})

If you’re using lightning:button, use the onclick event handler instead of the press event handler.
<aura:component>
<aura:attribute name="whichButton" type="String" />

<p>You clicked: {!v.whichButton}</p>

<lightning:button aura:id="button1" name="buttonname1" label="Click me"

onclick="{!c.nameThatButton}"/>
<lightning:button aura:id="button2" name="buttonname2" label="Click me"
onclick="{!c.nameThatButton}"/>
</aura:component>

In the client-side controller, you can use one of the following methods to find out which button was clicked.
• event.getSource().getLocalId() returns the aura:id of the clicked button.
• event.getSource().get("v.name") returns the name of the clicked button.

SEE ALSO:
Component IDs
Finding Components by ID

Formatting Dates in JavaScript

The AuraLocalizationService JavaScript API provides methods for formatting and localizing dates.
For example, the formatDate() method formats a date based on the formatString parameter set as the second argument.
formatDate (String | Number | Date date, String formatString)

The date parameter can be a String, Number, or most typically a JavaScript Date. If you provide a String value, use ISO 8601 format to
avoid parsing warnings.
The formatString parameter contains tokens to format a date and time. For example, "YYYY-MM-DD" formats 15th
January, 2017 as "2017-01-15". The default format string comes from the $Locale value provider.
This table shows the list of tokens supported in formatString.

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Creating Apps Formatting Dates in JavaScript

Description Token Output

Day of month d 1 … 31

Month M 1 ... 12

Month (short name) MMM Jan … Dec

Month (full name) MMMM January … December

Year y 2017

Year (identical to y) Y 2017

Year (two digit) YY 17

Year (four digit) YYYY 2017

Hour of day (1-12) h 1 … 12

Hour of day (0-23) H 0 … 23

Hour of day (1-24) k 1 … 24

Minute m 0 … 59

Second s 0 … 59

Fraction of second SSS 000 … 999

AM or PM a AM or PM

AM or PM (identical to a) A AM or PM

Zone offset from UTC Z -12:00 … +14:00

Quarter of year Q 1…4

Week of year w 1 … 53

Week of year (ISO) W 1 … 53

There are similar methods that differ in their default output values.
• formatDateTime()—The default formatString outputs datetime instead of date.
• formatDateTimeUTC()—Formats a datetime in UTC standard time.
• formatDateUTC()—Formats a date in UTC standard time.
For more information on all the methods in AuraLocalizationService, see the JavaScript API in the Reference Doc App.

Example: Use $A.localizationService to use the methods in AuraLocalizationService.

var now = new Date();
var dateString = "2017-01-15";

// Returns date in the format "Jun 8, 2017"

console.log($A.localizationService.formatDate(now));

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Creating Apps Using Java

// Returns date in the format "Jan 15, 2017"

console.log($A.localizationService.formatDate(dateString));

// Returns date in the format "2017 01 15"

console.log($A.localizationService.formatDate(dateString, "YYYY MM DD"));

// Returns date in the format "June 08 2017, 01:45:49 PM"

console.log($A.localizationService.formatDate(now, "MMMM DD YYYY, hh:mm:ss a"));

// Returns date in the format "Jun 08 2017, 01:48:26 PM"

console.log($A.localizationService.formatDate(now, "MMM DD YYYY, hh:mm:ss a"));

SEE ALSO:
Localization

Using Java
Use Java to write server-side Aura code. Services are the API in front of Aura. The Aura class is the entry point in Java for accessing
server-side services.
Your app can contain the following types of Java files.
• Models for initializing component data
• Server-side controllers for handling requests from client-side controllers
• Server-Side Providers for returning a concrete component at runtime for an abstract component or an interface in markup

IN THIS SECTION:
Essential Terminology
When you write Java code in Aura, it's essential to understand some basic concepts of the framework.
Reading Initial Component Data with Models
A model is a component's main source for dynamic data.
Creating Server-Side Logic with Controllers
The framework supports client-side and server-side controllers. An event is always wired to a client-side controller action, which can
in turn call a server-side controller action. For example, a client-side controller might handle an event and call a server-side controller
action to persist data to a database.
Server-Side Rendering to the DOM
The Aura rendering service takes in-memory component state and updates the component in the Document Object Model (DOM).
Server-Side Runtime Binding of Components
A provider enables you to use an abstract component in markup. The framework uses the provider to determine the concrete
component to use at runtime.

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Serializing Exceptions
You can serialize server-side exceptions and attach an event to be passed back to the client in such a way that an event is automatically
fired on the client side and handled by the client's error-handling event handler.

SEE ALSO:
Java Models
Creating Server-Side Logic with Controllers
Server-Side Runtime Binding of Components
Component Request Lifecycle
Using Object-Oriented Development

Essential Terminology
When you write Java code in Aura, it's essential to understand some basic concepts of the framework.

Term Description
Definition Each definition describes metadata for an element, such as a component, event, controller, or model. A
large part of Aura is a registry of definitions for its various elements.
A definition's metadata can include a name, location of origin, and descriptor (DefDescriptor, the primary
key of the definition).

DefDescriptor A DefDescriptor acts as a key for a definition in a registry. It's an Aura class that contains the metadata for
any definition used in Aura, such as a component, action, or event. In the example of a model, it is a nicely
parsed description of model="java://myPackage.MyClass" with methods to retrieve the
language, class name, and package name. Rather than passing a more heavyweight definition around in
code, Aura usually passes around a DefDescriptor instead.
The qualified name for a DefDescriptor has a format of either prefix://namespace:name or
prefix://namespace.name. For example, js://ui.button.
• prefix: Defines the language, such as JavaScript or Java
• namespace: Corresponds to the package name or XML namespace
• name: Corresponds to the class name or local name

Instance An instance represents the data for a component, event, or action. The component data is contained in its
model and attributes.

Registry Registries store metadata definitions. Some registries last for the duration of a request, while others are
cached for the lifetime of the app server. They may be created during the request process and destroyed
when the server completes the request. A master definition registry contains a list of registries for each Aura
resource.

Reading Initial Component Data with Models

A model is a component's main source for dynamic data.

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Creating Apps Reading Initial Component Data with Models

Use a model to read your initial component data and display the data on the user interface. You can create a model using Java or JSON.
For example, a Java model could read the component's data from a database. A JSON model reads your initial component data from a
JSON resource.

Java Models
Use a Java model to read a component's data from a dynamic source, such as a database. The component generates an appropriate
user interface from the model's data.
The value provider for a model is denoted by m. For example, the label in this button component is retrieved from the model of the
component containing the <ui:button> tag. The value for the label is evaluated when the component renders.
<ui:button label="{!m.myLabel}"/>

On the server side, Aura's model is more of a model initializer compared to the usage of models in other MVC frameworks. The model
is instantiated when the component is first requested. Perform any necessary operations to gather state, such as making database queries
or external API callouts, in the model's constructor.
When the component is serialized to the client, the @AuraEnabled getters are executed, and their results are serialized as name-value
pairs. This serialized map becomes the basis for the initial state of the model on the client.

Note: You can't create a new component dynamically in a model class using
Aura.getInstanceService().getInstance().

Wiring Up the Model

The aura:component tag contains a model system attribute that wires it to the Java model. For example:
<aura:component model="java://org.auraframework.demo.notes.models.TrivialModel">

Accessing the Model in Markup

Let's look at simple usage of a model in the markup of a component.
<aura:component model="java://org.auraframework.demo.notes.models.TrivialModel">
<aura:attribute name="name" type="String" required="true" default="Michelle" />

<!-- Use the "m." prefix to access any fields that are annotated with
@AuraEnabled in the model class -->
<h1>Title : {!m.title}</h1>

<!-- Use v.name to directly access the component's name attribute.

Remember that you use v to access the component's attribute values -->
<h2>Name : {!v.name}</h2>
</aura:component>

The {!m.title} expression returns the result of the getTitle() getter method in the component's model class. The
getTitle() method must be prefixed with the @AuraEnabled annotation.

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Java Model class

This model is simple as it doesn’t read in data from a persistent data store but it demonstrates some basics, including accessing a
component's attribute in the model.
package org.auraframework.demo.models;

import org.auraframework.instance.BaseComponent;
import org.auraframework.system.Annotations.AuraEnabled;
import org.auraframework.system.Annotations.Model;
import org.auraframework.throwable.quickfix.QuickFixException;

@Model
public class TrivialModel
{
private String title;

// The constructor is called during the construction of each instance of the model
// The constructor must be public
public TrivialModel() {
// This retrieves the component for this model as a Java object
BaseComponent cmp =
Aura.getContextService().getCurrentContext().getCurrentComponent();

// Retrieve the name attribute of the component

String name = (String)cmp.get("v.name");

/* Do any queries or data generation in the constructor of your model.

* In this sample, we have a trivial initialization for the title field.
* A real-world scenario would read the data from a persistent data store. */
title = "Welcome to " + name;
}

// Use @AuraEnabled to enable client- and server-side access to the title field
@AuraEnabled
public String getTitle() {
return title;
}
}

Java Annotations
These annotations are available in Java models.

Annotation Description
@Model Denotes that a Java class is a model.

@AuraEnabled Enables client- and server-side access to a getter method. This

means that you only expose data that you have explicitly annotated

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Annotation Description
and avoids accidentally exposing fields. Other fields are not
available.

SEE ALSO:
JSON Models
Accessing Models in JavaScript
Creating Server-Side Logic with Controllers
Server-Side Runtime Binding of Components
Mocking Java Models

JSON Models
Use a JSON model to read your initial component data in Aura from a JSON resource.
To initialize your component from a more dynamic source, such as a database, use a Java model instead.

Wiring Up the Model

There are a few ways to wire up a JSON model. A JSON model is auto-wired if it’s in the component bundle and follows the naming
convention, <componentName>Model.js.
You can explicitly declare a model in the aura:component tag by including a model system attribute with the format
model="js://<namespace>.<componentName>". This enables reuse of a model from another component. For example,
this component uses the auto-wired model for auradocs.sampleComponent in
auradocs/sampleComponent/sampleComponentModel.js.

<aura:component model="js://auradocs.sampleComponent

If you explicitly declare a model system attribute, it takes precedence over a model in the component bundle.

Note: A component can only have a JSON or Java model, but not both.

Sample JSON Model

Here is a sample JSON model.
{
"bool" : true,
"num" : 5,
"str" : "My name is JSON",
"list" : []
}

Note: Don't use null for model values. Use [] for an empty array, "" for an empty string, or zero for a number. This enables
the framework to determine which type of value wrapper to initialize. Due to a current limitation, don't use {} for an empty
object.

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Accessing the Model in Markup

Here is simple usage of a model in the markup of a component.
<-- This component uses an auto-wired model
as this aura:component tag has no model system attribute -->
<aura:component>
boolean: {!m.bool}
number: {!m.num}
string: {!m.str}
list length: {!m.list.length}
</aura:component>

SEE ALSO:
Java Models
Accessing Models in JavaScript
Component Bundles

Accessing Models in JavaScript

Use the value provider, m, to access a Java or JSON model in JavaScript code. For example:
var title = cmp.get("m.title");
alert("Title: " + title);

To update the model in JavaScript code, use set(). For example:

cmp.set("m.myLabel", "updated label");

SEE ALSO:
Java Models
JSON Models
Working with Attribute Values in JavaScript

Creating Server-Side Logic with Controllers

The framework supports client-side and server-side controllers. An event is always wired to a client-side controller action, which can in
turn call a server-side controller action. For example, a client-side controller might handle an event and call a server-side controller action
to persist data to a database.
Server-side actions need to make a round trip, from the client to the server and back again, so they usually complete more slowly than
client-side actions.
This diagram shows the flow from browser to client-side controller to server-side controller.

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The press attribute wires the button to the handlePress action of the client-side controller by using c.handlePress. The
client-side action name must match everything after the c.
For more details on the process of calling a server-side action, see Calling a Server-Side Action on page 203.

IN THIS SECTION:
Creating a Java Server-Side Controller
Create a server-side controller in Java. A component must include a controller attribute that wires it to the server-side Java
controller.
Calling a Server-Side Action
Call a server-side controller action from a client-side controller. In the client-side controller, you set a callback, which is called after
the server-side action is completed. A server-side action can return any object containing serializable JSON data.
Queueing of Server-Side Actions
The framework queues up actions before sending them to the server. This mechanism is largely transparent to you when you’re
writing code but it enables the framework to minimize network traffic by batching multiple actions into one request (XHR).
Foreground and Background Actions
Foreground actions are the default. An action can be marked as a background action. This is useful when you want your app to
remain responsive to a user while it executes a low priority, long-running action. A rough guideline is to use a background action if
it takes more than five seconds for the response to return from the server.

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Storable Actions
Enhance your component’s performance by marking actions as storable to quickly show cached data from client-side storage without
waiting for a server trip. If the cached data is stale, the framework retrieves the latest data from the server. Caching is especially
beneficial for users on high latency, slow, or unreliable connections such as 3G networks.
Abortable Actions
Mark an action as abortable to make it potentially abortable while it's queued to be sent to the server. An abortable action in the
queue is not sent to the server if the component that created the action is no longer valid, that is cmp.isValid() == false.
A component is automatically destroyed and marked invalid by the framework when it is unrendered.
Caboose Actions
Use a caboose server action to send data to the server that is not time-sensitive, such as logging, performance statistics, or click
tracking data.

Creating a Java Server-Side Controller

Create a server-side controller in Java. A component must include a controller attribute that wires it to the server-side Java
controller.
Here’s a sample Java controller that contains a serverEcho action that simply prepends a string to the value passed in. This is a
simple example that allows us to verify in the client that the value was returned by the server.
package org.auraframework.demo.controllers;

@ServiceComponent
public class SimpleServerSideController implements Controller
{

//Use @AuraEnabled to enable client- and server-side access to the method

@AuraEnabled
public static String serverEcho(@Key("firstName")String firstName) {
return ("From server: " + firstName);
}
}

Tip:
• Don't store component state in your controller. Store state in a component's attribute instead.
• Use unique names for client-side and server-side actions in a component. A JavaScript function (client-side action) with the
same name as a Java method (server-side action ) can lead to hard-to-debug issues. In PRODDEBUG mode, the framework
logs a browser console warning about the clashing client-side and server-side action names.

Java Annotations
These Java annotations are available in server-side controllers.
@ServiceComponent
Denotes that a Java class is a server-side controller. The class must implement the Controller interface too.
@AuraEnabled
Enables client- and server-side access to a controller method. This means that you only expose methods that you have explicitly
annotated.

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@Key
Sets a key for each argument in a method for a server-side action. When you use setParams to set parameters in the client-side
controller, match the JSON element name with the identifier for the @Key annotation. Note that we used a.setParams({
firstName : component.get("v.firstName") }); in the client-side controller that calls our sample server-side
controller.
The @Key annotation means that you don’t have to create an overloaded version of the method if you want to call it with different
numbers of arguments. The framework simply passes in null for any unspecified arguments.
You can also indicate which parameters are loggable by setting the optional second attribute, loggable, to true. This example
shows how to specify that the config and pageSize parameters should be included in the log:
public static Map<String, Object> refreshFeed(
@Key(value = "config", loggable = true) Object config,
@Key(value = "pageSize", loggable = true) Integer pageSize)
throws SQLException {
...
}

@BackgroundAction
Marks the action as a background action.

Wiring Up a Java Server-Side Controller

The component must include a controller attribute that wires it to the server-side Java controller. For example:
<aura:component
controller="java://org.auraframework.demo.controllers.SimpleServerSideController">

SEE ALSO:
Foreground and Background Actions
Component Markup

Calling a Server-Side Action

Call a server-side controller action from a client-side controller. In the client-side controller, you set a callback, which is called after the
server-side action is completed. A server-side action can return any object containing serializable JSON data.
A client-side controller is a JavaScript object in object-literal notation containing a map of name-value pairs.
Let’s say that you want to trigger a server-call from a component. The following component contains a button that’s wired to a client-side
controller echo action. SimpleServerSideController contains a method that returns a string passed in from the client-side
controller.
<aura:component
controller="java://org.auraframework.demo.controllers.SimpleServerSideController">
<aura:attribute name="firstName" type="String" default="world"/>
<lightning:button label="Call server" onclick="{!c.echo}"/>
</aura:component>

This client-side controller includes an echo action that executes a serverEcho method on a server-side controller.

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Tip: Use unique names for client-side and server-side actions in a component. A JavaScript function (client-side action) with the
same name as a Java method (server-side action ) can lead to hard-to-debug issues. In PRODDEBUG mode, the framework logs a
browser console warning about the clashing client-side and server-side action names.
({
"echo" : function(cmp) {
// create a one-time use instance of the serverEcho action
// in the server-side controller
var action = cmp.get("c.serverEcho");
action.setParams({ firstName : cmp.get("v.firstName") });

// Create a callback that is executed after

// the server-side action returns
action.setCallback(this, function(response) {
var state = response.getState();
if (state === "SUCCESS") {
// Alert the user with the value returned
// from the server
alert("From server: " + response.getReturnValue());

// You would typically fire a event here to trigger

// client-side notification that the server-side
// action is complete
}
else if (state === "INCOMPLETE") {
// do something
}
else if (state === "ERROR") {
var errors = response.getError();
if (errors) {
if (errors[0] && errors[0].message) {
console.log("Error message: " +
errors[0].message);
}
} else {
console.log("Unknown error");
}
}
});

// optionally set storable, abortable, background flag here

// A client-side action could cause multiple events,

// which could trigger other events and
// other server-side action calls.
// $A.enqueueAction adds the server-side action to the queue.
$A.enqueueAction(action);
}
})

In the client-side controller, we use the value provider of c to invoke a server-side controller action. We also use the c syntax in markup
to invoke a client-side controller action.
The cmp.get("c.serverEcho") call indicates that we’re calling the serverEcho method in the server-side controller. The
method name in the server-side controller must match everything after the c. in the client-side call. In this case, that’s serverEcho.

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Use action.setParams() to set data to be passed to the server-side controller. The following call sets the value of the firstName
argument on the server-side controller’s serverEcho method based on the firstName attribute value.
action.setParams({ firstName : cmp.get("v.firstName") });

action.setCallback() sets a callback action that is invoked after the server-side action returns.

action.setCallback(this, function(response) { ... });

The server-side action results are available in the response variable, which is the argument of the callback.
response.getState() gets the state of the action returned from the server.

Note: You don’t need a cmp.isValid() check in the callback in a client-side controller when you reference the component
associated with the client-side controller. The framework automatically checks that the component is valid.
response.getReturnValue() gets the value returned from the server. In this example, the callback function alerts the user
with the value returned from the server.
$A.enqueueAction(action) adds the server-side controller action to the queue of actions to be executed. All actions that are
enqueued will run at the end of the event loop. Rather than sending a separate request for each individual action, the framework
processes the event chain and batches the actions in the queue into one request. The actions are asynchronous and have callbacks. The
runAfter method is deprecated.

Tip: If your action is not executing, make sure that you’re not executing code outside the framework’s normal rerendering lifecycle.
For example, if you use window.setTimeout() in an event handler to execute some logic after a time delay, wrap your
code in $A.getCallback(). You don't need to use $A.getCallback() if your code is executed as part of the framework's
call stack; for example, your code is handling an event or in the callback for a server-side controller action.

Client Payload Data Limit

Use action.setParams() to set data for an action to be passed to a server-side controller.
The framework batches the actions in the queue into one server request. The request payload includes all of the actions and their data
serialized into JSON. The request payload limit is 4 MB.

IN THIS SECTION:
Action States
Call a server-side controller action from a client-side controller. The action can have different states during processing.

SEE ALSO:
Handling Events with Client-Side Controllers
Queueing of Server-Side Actions
Action States
Checking Component Validity

Action States
Call a server-side controller action from a client-side controller. The action can have different states during processing.
The possible action states are:
NEW
The action was created but is not in progress yet

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RUNNING
The action is in progress
SUCCESS
The action executed successfully
ERROR
The server returned an error
INCOMPLETE
The server didn’t return a response. The server might be down or the client might be offline. The framework guarantees that an
action’s callback is always invoked as long as the component is valid. If the socket to the server is never successfully opened, or closes
abruptly, or any other network error occurs, the XHR resolves and the callback is invoked with state equal to INCOMPLETE.
ABORTED
The action was aborted. This action state is deprecated. A callback for an aborted action is never executed so you can’t do anything
to handle this state.

SEE ALSO:
Calling a Server-Side Action

Queueing of Server-Side Actions

The framework queues up actions before sending them to the server. This mechanism is largely transparent to you when you’re writing
code but it enables the framework to minimize network traffic by batching multiple actions into one request (XHR).
The batching of actions is also known as boxcar’ing, similar to a train that couples boxcars together.
The framework uses a stack to keep track of the actions to send to the server. When the browser finishes processing events and JavaScript
on the client, the enqueued actions on the stack are sent to the server in a batch.

Tip: If your action is not executing, make sure that you’re not executing code outside the framework’s normal rerendering lifecycle.
For example, if you use window.setTimeout() in an event handler to execute some logic after a time delay, wrap your
code in $A.getCallback().
There are some properties that you can set on an action to influence how the framework manages the action while it’s in the queue
waiting to be sent to the server. For more information, see:
• Foreground and Background Actions on page 206
• Storable Actions on page 208
• Abortable Actions on page 211
• Caboose Actions on page 211

SEE ALSO:
Modifying Components Outside the Framework Lifecycle

Foreground and Background Actions

Foreground actions are the default. An action can be marked as a background action. This is useful when you want your app to remain
responsive to a user while it executes a low priority, long-running action. A rough guideline is to use a background action if it takes more
than five seconds for the response to return from the server.

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Batching of Actions
Multiple queued foreground actions are batched in a single request (XHR) to minimize network traffic. The batching of actions is also
known as boxcar’ing, similar to a train that couples boxcars together.
The server sends the XHR response to the client when all actions have been processed on the server. If a long-running action is in the
boxcar, the XHR response is held until that long-running action completes. Marking an action as background results in that action being
sent separately from any foreground actions. The separate transmission ensures that the background action doesn’t impact the response
time of the foreground actions.
When the server-side actions in the queue are executed, the foreground actions execute first and then the background actions execute.
Background actions run in parallel with foreground actions and responses of foreground and background actions may come back in
either order.
We don’t make any guarantees for the order of execution of action callbacks. XHR responses may return in a different order than the
order in which the XHR requests were sent due to server processing time.

Note: Don’t rely on each background action being sent in its own request as that behavior isn’t guaranteed and it can lead to
performance issues. Remember that the motivation for background actions is to isolate long-running requests into a separate
request to avoid slowing the response for foreground actions.
If two actions must be executed sequentially, the component must orchestrate the ordering. The component can enqueue the first
action. In the first action’s callback, the component can then enqueue the second action.

Framework-Managed Request Throttling

The framework throttles foreground and background requests separately. This means that the framework can control the number of
foreground requests and the number of background actions running at any time. The framework automatically throttles requests and
it’s not user controlled. The framework manages the number of foreground and background XHRs, which varies depending on available
resources.
Even with separate throttling, background actions might affect performance in some conditions, such as an excessive number of requests
to the server.

Setting Background Actions

To set an action as a background action, call the setBackground() method on the action object in JavaScript.
// set up the server-action action
var action = cmp.get("c.serverEcho");
// optionally set actions params
//action.setParams({ firstName : cmp.get("v.firstName") });
// set as a background action
action.setBackground();

Note: A background action can’t be set back to a foreground action. In other words, calling setBackground to set it to
false will have no effect.

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To mark a server-side action as a background action in Java, use the @BackgroundAction annotation at the method level on the
controller. If you set @BackgroundAction in Java, you don’t need to set action.setBackground() in JavaScript code.

SEE ALSO:
Queueing of Server-Side Actions
Calling a Server-Side Action
Creating a Java Server-Side Controller

Storable Actions
Enhance your component’s performance by marking actions as storable to quickly show cached data from client-side storage without
waiting for a server trip. If the cached data is stale, the framework retrieves the latest data from the server. Caching is especially beneficial
for users on high latency, slow, or unreliable connections such as 3G networks.

Warning:
• A storable action might result in no call to the server. Never mark as storable an action that updates or deletes data.
• For storable actions in the cache, the framework returns the cached response immediately and also refreshes the data if it’s
stale. Therefore, storable actions might have their callbacks invoked more than once: first with cached data, then with updated
data from the server.

Most server requests are read-only and idempotent, which means that a request can be repeated or retried as often as necessary without
causing data changes. The responses to idempotent actions can be cached and quickly reused for subsequent identical actions. For
storable actions, the key for determining an identical action is a combination of:
• Java controller name
• Method name
• Method parameter values

Marking an Action as Storable

To mark a server-side action as storable, call setStorable() on the action in JavaScript code, as follows.
action.setStorable();

Note: Storable actions are always implicitly marked as abortable too.

The setStorable function takes an optional argument, which is a configuration map of key-value pairs representing the storage
options and values to set. You can only set the following property:
ignoreExisting
Set to true to bypass the cache. The default value is false.
This property is useful when you know that any cached data is invalid, such as after a record modification. This property should be
used rarely because it explicitly defeats caching.
To set the storage options for the action response, pass this configuration map into setStorable(configObj).

IN THIS SECTION:
Lifecycle of Storable Actions
This image describes the sequence of callback execution for storable actions.

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Enable Storable Actions in an Application

To use storable actions in a standalone app (.app resource), you must configure client-side storage for cached action responses.

SEE ALSO:
Calling a Server-Side Action
Lifecycle of Storable Actions
Creating Server-Side Logic with Controllers
Abortable Actions

Lifecycle of Storable Actions

This image describes the sequence of callback execution for storable actions.

Note: An action might have its callback invoked more than once:
• First with the cached response, if it’s in storage.
• Second with updated data from the server, if the stored response has exceeded the time to refresh entries.

Cache Miss
If the action is not a cache hit as it doesn’t match a storage entry:
1. The action is sent to the server-side controller.
2. If the response is SUCCESS, the response is added to storage.
3. The callback in the client-side controller is executed.
The Action object in JavaScript provides methods to determine if the response is from storage or if it's the result of a storage
refresh.
action.isFromStorage() // returns false
action.isRefreshAction() // returns false

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Cache Hit
If the action is a cache hit as it matches a storage entry:
1. The callback in the client-side controller is executed with the cached action response.
The Action object returns these values:
action.isFromStorage() // returns true
action.isRefreshAction() // returns false

2. If the response has been cached for longer than the refresh time, the storage entry is refreshed.
When an application enables storable actions, a refresh time is configured. The refresh time is the duration in seconds before an
entry is refreshed in storage. The refresh time is automatically configured in Lightning Experience and the Salesforce mobile app.

3. The action is sent to the server-side controller.

4. If the response is SUCCESS, the response is added to storage.
5. If the refreshed response is different from the cached response, the callback in the client-side controller is executed for a second
time.
The Action object returns these values:
action.isFromStorage() // returns false
action.isRefreshAction() // returns true

SEE ALSO:
Storable Actions
Enable Storable Actions in an Application

Enable Storable Actions in an Application

To use storable actions in a standalone app (.app resource), you must configure client-side storage for cached action responses.
To configure client-side storage for your standalone app, use <auraStorage:init> in the auraPreInitBlock attribute of
your application’s template. For example:
<aura:component isTemplate="true" extends="aura:template">
<aura:set attribute="auraPreInitBlock">
<auraStorage:init
name="actions"
persistent="false"
secure="true"
maxSize="1024"
defaultExpiration="900"
defaultAutoRefreshInterval="30" />
</aura:set>
</aura:component>

name
The name for the storage instance.
persistent
Set to true to preserve cached data between user sessions in the browser.

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secure
Set to true to encrypt cached data.
maxsize
The maximum size in KB of the storage.
defaultExpiration
The duration in seconds that an entry is retained in storage.
defaultAutoRefreshInterval
The duration in seconds before an entry is refreshed in storage.
Storable actions use the Storage Service. The Storage Service supports multiple implementations of storage and selects an adapter at
runtime based on browser support and specified characteristics of persistence and security.

SEE ALSO:
Initializing Storage Service
Storage Service Adapters

Abortable Actions
Mark an action as abortable to make it potentially abortable while it's queued to be sent to the server. An abortable action in the queue
is not sent to the server if the component that created the action is no longer valid, that is cmp.isValid() == false. A component
is automatically destroyed and marked invalid by the framework when it is unrendered.

Note: We recommend that you only use abortable actions for read-only operations as they are not guaranteed to be sent to the
server.
An abortable action is sent to the server and executed normally unless the component that created the action is invalid before the action
is sent to the server.
A non-abortable action is always sent to the server and can't be aborted in the queue.
If an action response returns from the server and the associated component is now invalid, the logic has been executed on the server
but the action callback isn’t executed. This is true whether or not the action is marked as abortable.

Marking an Action as Abortable

Mark a server-side action as abortable by using the setAbortable() method on the Action object in JavaScript. For example:
var action = cmp.get("c.serverEcho");
action.setAbortable();

SEE ALSO:
Creating Server-Side Logic with Controllers
Queueing of Server-Side Actions
Calling a Server-Side Action

Caboose Actions
Use a caboose server action to send data to the server that is not time-sensitive, such as logging, performance statistics, or click tracking
data.

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A caboose action waits until another non-caboose foreground action is sent and will piggyback on that XMLHttpRequest (XHR).
This can improve performance by eliminating the overhead of additional round trips to the server.
If no other actions trigger an XHR to be sent to the server within 60 seconds, any pending caboose actions are batched into their own
XHR. The 60-seconds countdown starts when a caboose action is enqueued. The caboose action is sent the next time the framework
processes any events after the countdown elapses.

Note: If there is a caboose action in the queue when a user closes the app, that caboose action will not be sent.

Marking Caboose Actions

When you generate data on the client that you want to send to the server, mark a foreground action as a caboose action with
action.setCaboose(), set a callback with setAllAboardCallback(), and enqueue the action using
$A.enqueueAction(). The setAllAboardCallback() callback is called just before the action is sent to the server, just
like an “all aboard” announcement before a train leaves a station.
To implement a log and flush pattern, the callback should use one or more calls to setParam() on the action to set the data to be
sent. The server-side action should then process the data that was sent as parameters.
This sample code in a helper adds log data to a data queue. The caboose action contains the log data and flushes the client-side data
queue just before the action is sent to the server.
({
initFields : function(component) {
/**
* A queue of log data objects
*/
this.dataQueue = [];
},

/**
* Add log data to the data queue
*
* @param {!string} key App analytics handler key
* @param {!Object} data App analytics data
*/
doCaboose : function(key, data) {
// if data queue is empty, set up caboose action
if (this.dataQueue.length == 0) {
// set server-side action
// serverHandle is a method in the server-side controller
// that processes the data. The server-side code is not shown here.
var action = component.get('c.serverHandle');
action.setAllAboardCallback(this,
this.flushDataQueue);
action.setCaboose();
$A.enqueueAction(action);
}
var logData = {};
logData[key] = data;
this.dataQueue.push(logData);
},

/**
* Send the queue to the server and then reset the queue

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*
* @param {!Object} action Caboose action that is about to be sent to the server
*/
flushDataQueue : function(action) {
var batchedData = this.dataQueue;
this.dataQueue = [];
action.setParam('batch', batchedData);
}
})

SEE ALSO:
Queueing of Server-Side Actions
Calling a Server-Side Action

Server-Side Rendering to the DOM

The Aura rendering service takes in-memory component state and updates the component in the Document Object Model (DOM).
The DOM is the language-independent model for representing and interacting with objects in HTML and XML documents. Aura
automatically renders your components so you don't have to know anything more about rendering unless you need to customize the
default rendering behavior for a component.

Note: The preferred way to customize component rendering is to use a client-side renderer. You can also use a server-side renderer
but it's not recommended as they don't degrade gracefully if an error, such as a network connection outage, occurs. The framework
uses a server-side renderer to render an app's template and that is the primary use case for rendering on the server.

Creating a Java Server-Side Renderer

If you've exhausted the alternatives, including a client-side renderer, create a server-side renderer in Java by implementing the
org.auraframework.def.Renderer interface. The interface contains one method:

public void render(BaseComponent<?,?> component, Appendable appendable)

throws IOException, QuickFixException;

The component argument is the instance to render. The appendable argument is the output buffer.
The class that implements the interface must have a no-argument constructor. The class is instantiated as a singleton, so no state should
be stored in it.

Wiring Up a Server-Side Renderer

To wire up a server-side renderer for a component, add a renderer system attribute in <aura:component>. For example:
<aura:component
renderer="java://org.auraframework.demo.notes.renderers.ReallyNeedAServerSideRenderer">
...
</aura:component>

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The framework behavior is undefined if you add a server-side renderer that also includes a client-side renderer. We recommend that
you use one or the other.

SEE ALSO:
Create a Custom Renderer
Creating App Templates

Server-Side Runtime Binding of Components

A provider enables you to use an abstract component in markup. The framework uses the provider to determine the concrete component
to use at runtime.
Server-side providers are more common, but if you don't need to access the server when you're creating a component, you can use a
client-side provider instead.
Set the provider system attribute in the <aura:component> tag of an abstract component to point to the server-side provider
Java class.
The syntax of the provider system attribute is provider="java://package.class" where package.class is the
fully qualified name for the class.
A Java provider must:
• Include the @Provider annotation above the class definition
• Implement either the ComponentDescriptorProvider or ComponentConfigProvider interface
At runtime, a provider has access to a shell of the abstract component, including any attribute values that have been set. The model isn't
constructed yet so you can't access it. The provide() method can examine the attribute values that are set on the component, and
return a descriptor of the non-abstract component type that should be used.

Note: A provider should only return concrete components that are sub-components of a single base component that implement
an interface. Aura doesn't currently enforce this restriction, but it’s the preferred pattern. The abstract component that references
the provider also extends the base component.

ComponentDescriptorProvider
Use the ComponentDescriptorProvider interface to return a DefDescriptor describing the concrete component to
use when you don’t need to set attributes for the component. For example:
@Provider
public class SampleDescProvider implements ComponentDescriptorProvider {

public DefDescriptor<ComponentDef> provide() {

DefDescriptor defDesc = null;

// logic to determine DefDescriptor to set and return.

return defDesc;
}
}

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ComponentConfigProvider
Use the ComponentConfigProvider interface to return a ComponentConfig, which describes the concrete component
to use in a DefDescriptor and enables you to set attributes for the component. For example:
@Provider
public class SampleConfigProvider implements ComponentConfigProvider {

public ComponentConfig<ComponentDef> provide() {

ComponentConfig cmpConfig = null;

// logic to determine DefDescriptor

// and attributes to set.

return cmpConfig;
}
}

Declaring Provider Dependencies

The Aura framework automatically tracks dependencies between definitions, such as components. However, if a component uses a
provider that instantiates components that are not directly referenced elsewhere, use <aura:dependency> in the component to
explicitly tell the framework about the dependency, which wouldn't otherwise be discovered by Aura.

SEE ALSO:
Client-Side Runtime Binding of Components
Abstract Components
Interfaces
Getting a Java Reference to a Definition
aura:dependency
Mocking Java Providers

Serializing Exceptions
You can serialize server-side exceptions and attach an event to be passed back to the client in such a way that an event is automatically
fired on the client side and handled by the client's error-handling event handler.
To do this, on the server, instantiate a GenericEventException that contains an event and parameters and then throw it. The
exception gets serialized and when the action goes back to the client, the exception is sent along with the action as an error on the
action. The status of the action will be set as “Error”. The specified event in GenericEventException will be fired and its handlers
invoked. If a callback is provided specifically for the error state, then that callback is invoked. Otherwise, the default callback is invoked.
@AuraEnabled
public static void throwsGEE(@Key("event") String event, @Key("paramName") String paramName,

@Key("paramValue") String paramValue) throws Throwable {

GenericEventException gee = new GenericEventException(event);
if (paramName != null) {
gee.addParam(paramName, paramValue);
}

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Creating Apps Java Cookbook

throw gee;
}

On the client, the client-side framework automatically handles deserializing the event and firing it. For a component event, only handlers
associated with this component are invoked, else the firing of the event has no effect. For an application event, its global and all event
handlers are invoked.
A GenericEventException is a server-side Java exception that extends the generic exception,
ClientSideEventException. Optionally, you can extend ClientSideEventException yourself but it is easier to use
the provided GenericEventException. Other classes that extend ClientSideEventException are the
ClientOutOfSyncException class, the SystemErrorException class, the InvalidSessionException class,
and the NoAccessException class. These classes are for internal use only.
For a working example of a server-side controller that throws a GenericEventException, refer to the test:testActionEvent
component.

SEE ALSO:
Creating Server-Side Logic with Controllers

Java Cookbook
This section includes code snippets and samples that can be used in JavaScript classes.

IN THIS SECTION:
Dynamically Creating Components in Java
You can create a component dynamically in your Java code.
Setting a Component ID
To create a component with a local ID and attributes in Java code, use ComponentDefRefBuilder to set the component
definition reference.
Getting a Java Reference to a Definition
A definition in Aura describes metadata for an object, such as a component, event, controller, or model. Rather than passing a more
heavyweight definition around in code, Aura usually passes around a reference, called a DefDescriptor, instead.

Dynamically Creating Components in Java

You can create a component dynamically in your Java code.
This example demonstrates how to use Java to get an instance of a component. An instance represents the data for a component. Use
the InstanceService class to create a new component instance.
// listAttributes is a map of attributes for the component
Map<String, Object> listAttributes = new HashMap();
listAttributes.put("sort", "asc");
Component cmpInstance =
Aura.getInstanceService().getInstance("auranote:noteList",
ComponentDef.class, listAttributes);

The first parameter to the getInstance method is auranote:noteList, which is the qualified name for a noteList
component in the auranote namespace.

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The second parameter is ComponentDef.class, which indicates the class for the instance.
The third parameter is listAttributes, which contains a map of attributes for the component instance. In this case, we only have
one sort attribute, but you can add more attributes to the map, if needed.
The InstanceService class also has other overloaded getInstance methods that take either a Definition or a
DefDescriptor as their first parameter instead of a qualified name.

SEE ALSO:
Setting a Component ID
Component Request Glossary
Getting a Java Reference to a Definition

Setting a Component ID
To create a component with a local ID and attributes in Java code, use ComponentDefRefBuilder to set the component definition
reference.
ComponentDefRefBuilder is also known as ComponentDefRef. The ComponentDefRef creates the definition of the
component instance and turns it into an instance of the component during runtime. For example, the aura:if component uses
ComponentDefRef for its body and else attributes.

ComponentDefRefBuilder builder = Aura.getBuilderService().getComponentDefRefBuilder();

//Set the descriptor for your new component

builder.setDescriptor("namespace:newCmp");

//Set the local Id for your new component

builder.setLocalId("newId");

//Set attributes on the new component

builder.setAttribute("attr1", false);
builder.setAttribute("attr2", attrVal);

//Create a new instance of the component

Component aNewCmp = builder.build().newInstance(null).get(0);

You can also create an instance of a component using Aura.getInstanceService().getInstance(), but you should
use the ComponentDefRefBuilder if you want to:
• Set an ID on the new component.
• Set a facet on a top-level component.
• Create multiple instances of the components with minimal updates to the definition.
The XML Parser in Aura reads in files, such as .cmp, .intf, and .evt, by using the BuilderService to construct definitions.
The BuilderService doesn't know anything about XML. If you want to create reusable definitions that are the equivalent of what
you could type into an XML file, but don't want to use XML as the storage format, use the BuilderService.

Note: Although ComponentDefRef provides performance benefits, we recommend you to use AuraComponent[]
instead as ComponentDefRef will be deprecated in a later release. During component creation, any items marked as an
AuraComponent[] type is recursively created. Items that are marked as a ComponentDefRef is initialized as a list that

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contains only the information to create the actual components at a later time. For more information, see Component Request
Lifecycle.

SEE ALSO:
Component Facets
Dynamically Creating Components in Java
Component Request Glossary
Server-Side Processing for Component Requests

Getting a Java Reference to a Definition

A definition in Aura describes metadata for an object, such as a component, event, controller, or model. Rather than passing a more
heavyweight definition around in code, Aura usually passes around a reference, called a DefDescriptor, instead.
In the example of a model, a DefDescriptor is a nicely parsed description of model="java://myPackage.MyClass"
with methods to retrieve the language, class name, and package name.
To create a DefDescriptor in Java code, use the DefinitionService class to create a new DefDescriptor.
DefDescriptor<ComponentDef> defDesc =
Aura.getDefinitionService().getDefDescriptor("ui:button", ComponentDef.class);

The first parameter to the getDefDescriptor method is ui:button, which is the qualified name for a button component in
the ui namespace. The second parameter is ComponentDef.class, which indicates the class for the definition.

SEE ALSO:
Component Request Glossary

Lightning Container
Upload an app developed with a third-party framework as a static resource, and host the content in a Lightning component using
lightning:container. Use lightning:container to use third-party frameworks like AngularJS or React within your
Lightning pages.
The lightning:container component hosts content in an iframe. You can implement communication to and from the framed
application, allowing it to interact with the Lightning component. lightning:container provides the message() method,
which you can use in the JavaScript controller to send messages to the application. In the component, specify a method for handling
messages with the onmessage attribute.

IN THIS SECTION:
Lightning Container Component Limits
Understand the limits of lightning:container.
The Lightning Realty App
The Lightning Realty App is a more robust example of messaging between the Lightning Container Component and Salesforce.
lightning-container NPM Module Reference
Use methods included in the lightning-container NPM module in your JavaScript code to send and receive messages to and from
your custom Lightning component, and to interact with the Salesforce REST API.

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Using a Third-Party Framework

lightning:container allows you to use an app developed with a third-party framework, such as AngularJS or React, in a Lightning
component. Upload the app as a static resource.
Your application must have a launch page, which is specified with the lightning:container src attribute. By convention, the
launch page is index.html, but you can specify another launch page by adding a manifest file to your static resource. The following
example shows a simple Lightning component that references myApp, an app uploaded as a static resource, with a launch page of
index.html.

<aura:component>
<lightning:container src="{!$Resource.myApp + '/index.html'}" />
</aura:component>

The contents of the static resource are up to you. It should include the JavaScript that makes up your app, any associated assets, and a
launch page.
As in other Lightning components, you can specify custom attributes. This example references the same static resource, myApp, and
has three attributes, messageToSend, messageReceived, and error. Because this component includes
implements="flexipage:availableForAllPageTypes", it can be used in the Lightning App Builder and added to
Lightning pages.

Note: The examples in this section are accessible on the Developerforce Github Repository.

<aura:component access="global" implements="flexipage:availableForAllPageTypes" >

<aura:attribute access="private" name="messageToSend" type="String" default=""/>
<aura:attribute access="private" name="messageReceived" type="String" default=""/>
<aura:attribute access="private" name="error" type="String" default=""/>

<div>
<lightning:input name="messageToSend" value="{!v.messageToSend}" label="Message
to send to React app: "/>
<lightning:button label="Send" onclick="{!c.sendMessage}"/>
<br/>
<lightning:textarea value="{!v.messageReceived}" label="Message received from React
app: "/>
<br/>
<aura:if isTrue="{! !empty(v.error)}">
<lightning:textarea name="errorTextArea" value="{!v.error}" label="Error: "/>

</aura:if>

<lightning:container aura:id="ReactApp"
src="{!$Resource.SendReceiveMessages + '/index.html'}"
onmessage="{!c.handleMessage}"
onerror="{!c.handleError}"/>
</div>
</aura:component>

The component includes a lightning:input element, allowing users to enter a value for messageToSend. When a user hits
Send, the component calls the controller method sendMessage. This component also provides methods for handling messages
and errors.

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This snippet doesn’t include the component’s controller or other code, but don’t worry. We’ll dive in, break it down, and explain how to
implement message and error handling as we go in Sending Messages from the Lightning Container Component and Handling Errors
in Your Container.

SEE ALSO:
Lightning Container
Sending Messages from the Lightning Container Component
Handling Errors in Your Container

Sending Messages from the Lightning Container Component

Use the onmessage attribute of lightning:container to specify a method for handling messages to and from the contents
of the component—that is, the embedded app. The contents of lightning:container are wrapped within an iframe, and this
method allows you to communicate across the frame boundary.
This example shows a Lightning component that includes lightning:container and has three attributes, messageToSend,
messageReceived, and error.
This example uses the same code as the one in Using a Third-Party Framework. You can download the complete version of this example
from the Developerforce Github Repository.
<aura:component access="global" implements="flexipage:availableForAllPageTypes" >
<aura:attribute access="private" name="messageToSend" type="String" default=""/>
<aura:attribute access="private" name="messageReceived" type="String" default=""/>
<aura:attribute access="private" name="error" type="String" default=""/>

<div>
<lightning:input name="messageToSend" value="{!v.messageToSend}" label="Message
to send to React app: "/>
<lightning:button label="Send" onclick="{!c.sendMessage}"/>
<br/>
<lightning:textarea value="{!v.messageReceived}" label="Message received from React
app: "/>
<br/>
<aura:if isTrue="{! !empty(v.error)}">
<lightning:textarea name="errorTextArea" value="{!v.error}" label="Error: "/>

</aura:if>

<lightning:container aura:id="ReactApp"
src="{!$Resource.SendReceiveMessages + '/index.html'}"
onmessage="{!c.handleMessage}"
onerror="{!c.handleError}"/>
</div>
</aura:component>

messageToSend represents a message sent from Salesforce to the framed app, while messageReceived represents a message
sent by the app to the Lightning component. lightning:container includes the required src attribute, an aura:id, and
the onmessage attribute. The onmessage attribute specifies the message-handling method in your JavaScript controller, and the
aura:id allows that method to reference the component.

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This example shows the component’s JavaScript controller.

({
sendMessage : function(component, event, helper) {

var msg = {
name: "General",
value: component.get("v.messageToSend")
};
component.find("ReactApp").message(msg);
},

handleMessage: function(component, message, helper) {

var payload = message.getParams().payload;
var name = payload.name;
if (name === "General") {
var value = payload.value;
component.set("v.messageReceived", value);
}
else if (name === "Foo") {
// A different response
}
},

handleError: function(component, error, helper) {

var e = error;
}
})

This code does a couple of different things. The sendMessage action sends a message from the enclosing Lightning component to
the embedded app. It creates a variable, msg, that has a JSON definition including a name and a value. This definition of the message
is user-defined—the message’s payload can be a value, a structured JSON response, or something else. The messageToSend attribute
of the Lightning component populates the value of the message. The method then uses the component’s aura:id and the
message() function to send the message back to the Lightning component.
The handleMessage method receives a message from the embedded app and handles it appropriately. It takes a component, a
message, and a helper as arguments. The method uses conditional logic to parse the message. If this is the message with the name
and value we’re expecting, the method sets the Lightning component’s messageReceived attribute to the value of the
message. Although this code only defines one message, the conditional statement allows you to handle different types of message,
which are defined in the sendMessage method.
The handler code for sending and receiving messages can be complicated. It helps to understand the flow of a message between the
Lightning component, its controller, and the app. The process begins when user enters a message as the messageToSend attribute.
When the user clicks Send, the component calls sendMessage. sendMessage defines the message payload and uses the
message() method to send it to the app. Within the static resource that defines the app, the specified message handler function
receives the message. Specify the message handling function within your JavaScript code using the lightning-container module’s
addMessageHandler() method. See the lightning-container NPM Module Reference for more information.
When lightning:container receives a message from the framed app, it calls the component controller’s handleMessage
method, as set in the onmessage attribute of lightning:container. The handleMessage method takes the message,
and sets its value as the messageReceived attribute. Finally, the component displays messageReceived in a
lightning:textarea.

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This is a simple example of message handling across the container. Because you implement the controller-side code and the functionality
of the app, you can use this functionality for any kind of communication between Salesforce and the app embedded in
lightning:container.

Important: Don't send cryptographic secrets like an API key in a message. It's important to keep your API key secure.

SEE ALSO:
Lightning Container
Using a Third-Party Framework
Handling Errors in Your Container

Sending Messages to the Lightning Container Component

Use the methods in the lightning-container NPM module to send messages from the JavaScript code framed by
lightning:container.
The Lightning-container NPM module provides methods to send and receive messages between your JavaScript app and the Lightning
container component. You can see the lightning-container module on the NPM website.
Add the lightning-container module as a dependency in your code to implement the messaging framework in your app.
import LCC from 'lightning-container';

lightning-container must also be listed as a dependency in your app’s package.json file.

The code to send a message to lightning:container from the app is simple. This code corresponds to the code samples in
Sending Messages from the Lightning Container Component and Handling Errors in Your Container, and can be downloaded from the
Developerforce Github Repository.
sendMessage() {
LCC.sendMessage({name: "General", value: this.state.messageToSend});
}

This code, part of the static resource, sends a message as an object containing a name and a value, which is user-defined.
When the app receives a message, it’s handled by the function mounted by the addMessageHandler() method. In a React app,
functions must be mounted to be part of the document-object model and rendered in the output.
The lightning-container module provides similar methods for defining a function to handle errors in the messaging framework. For more
information, see lightning-container NPM Module Reference

Important: Don't send cryptographic secrets like an API key in a message. It's important to keep your API key secure.

Handling Errors in Your Container

Handle errors in Lightning container with a method in your component’s controller.
This example uses the same code as the examples in Using a Third-Party Framework and Sending Messages from the Lightning Container
Component.
In this component, the onerror attribute of lightning:container specifies handleError as the error handling method.
To display the error, the component markup uses a conditional statement, and another attribute, error, for holding an error message.
<aura:component access="global" implements="flexipage:availableForAllPageTypes" >

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<aura:attribute access="private" name="messageToSend" type="String" default=""/>

<aura:attribute access="private" name="messageReceived" type="String" default=""/>
<aura:attribute access="private" name="error" type="String" default=""/>

<div>
<lightning:input name="messageToSend" value="{!v.messageToSend}" label="Message
to send to React app: "/><lightning:button label="Send" onclick="{!c.sendMessage}"/>

<br/>

<lightning:textarea name="messageReceived" value="{!v.messageReceived}"

label="Message received from React app: "/>

<br/>

<aura:if isTrue="{! !empty(v.error)}">

<lightning:textarea name="errorMessage" value="{!v.error}" label="Error: "/>
</aura:if>

<lightning:container aura:id="ReactApp"
src="{!$Resource.SendReceiveMessages + '/index.html'}"
onmessage="{!c.handleMessage}"
onerror="{!c.handleError}"/>
</div>

</aura:component>

This is the component’s controller.

({
sendMessage : function(component, event, helper) {

var msg = {
name: "General",
value: component.get("v.messageToSend")
};
component.find("ReactApp").message(msg);
},

handleMessage: function(component, message, helper) {

var payload = message.getParams().payload;
var name = payload.name;
if (name === "General") {
var value = payload.value;
component.set("v.messageReceived", value);
}
else if (name === "Foo") {
// A different response
}
},

handleError: function(component, error, helper) {

var description = error.getParams().description;
component.set("v.error", description);

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}
})

If the Lightning container application throws an error, the error handling function sets the error attribute. Then, in the component
markup, the conditional expression checks if the error attribute is empty. If it isn’t, the component populates a lightning:textarea
element with the error message stored in error.

SEE ALSO:
Lightning Container
Using a Third-Party Framework
Sending Messages from the Lightning Container Component

Using Apex Services from Your Container

Use the lightning-container NPM module to call Apex methods from your Lightning container component.
To call Apex methods from lightning:container, you must set the CSP level to low in the manifest.json file. A CSP
level of low allows the Lightning container component load resources from outside of the Lightning domain.
This is a Lightning component that including a Lightning container component that uses Apex services:
<aura:component access="global" implements="flexipage:availableForAllPageTypes">

<aura:attribute access="private" name="error" type="String" default=""/>

<div>
<aura:if isTrue="{! !empty(v.error)}">
<lightning:textarea name="errorTextArea" value="{!v.error}" label="Error: "/>

</aura:if>

<lightning:container aura:id="ReactApp"
src="/ApexController/index.html"
onerror="{!c.handleError}"/>
</div>

</aura:component>

This is the component’s controller:

({
handleError: function(component, error, helper) {
var description = error.getParams().description;
component.set("v.error", description);
}
})

Note: You can download the complete version of this example from the Developerforce Github Repository.

There’s not a lot going on in the component’s JavaScript controller—the real action is in the JavaScript app, uploaded as a static resource,
that the Lightning container references.
import React, { Component } from 'react';
import LCC from "lightning-container";

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import logo from './logo.svg';

import './App.css';

class App extends Component {

callApex() {
LCC.callApex("lcc1.ApexController.getAccount",
this.state.name,
this.handleAccountQueryResponse,
{escape: true});
}

handleAccountQueryResponse(result, event) {
if (event.status) {
this.setState({account: result});
}
else if (event.type === "exception") {
console.log(event.message + " : " + event.where);
}
}

render() {
var account = this.state.account;

return (
<div className="App">
<div className="App-header">
<img src={logo} className="App-logo" alt="logo" />
<h2>Welcome to LCC</h2>
</div>
<p className="App-intro">
Account Name: <input type="text" id="accountName" value={this.state.name}
onChange={e => this.onAccountNameChange(e)}/><br/>
<input type="submit" value="Call Apex Controller" onClick={this.callApex}/><br/>

Id: {account.Id}<br/>
Phone: {account.Phone}<br/>
Type: {account.Type}<br/>
Number of Employees: {account.NumberOfEmployees}<br/>
</p>
</div>
);
}

constructor(props) {
super(props);
this.state = {
name: "",
account: {}
};

this.handleAccountQueryResponse = this.handleAccountQueryResponse.bind(this);
this.onAccountNameChange = this.onAccountNameChange.bind(this);
this.callApex = this.callApex.bind(this);

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Creating Apps Lightning Container Component Limits

onAccountNameChange(e) {
this.setState({name: e.target.value});
}
}

export default App;

The first function, callApex(), uses the LCC.callApex method to call getAccount, an Apex method that gets and displays
an account’s information.

Lightning Container Component Limits

Understand the limits of lightning:container.
lightning:container has known limitations. You might observe performance and scrolling issues associated with the use of
iframes. This component isn’t designed for the multi-page model, and it doesn’t integrate with browser navigation history.
If you navigate away from the page and a lightning:container component is on, the component doesn’t automatically
remember its state. The content within the iframe doesn’t use the same offline and caching schemes as the rest of Lightning Experience.
Creating a Lightning app that loads a Lightning container static resource from another namespace is not supported. If you install a
package, your apps should use the custom Lightning components published by that package, not their static resources directly. Any
static resource you use as the lightning:container src attribute should have your own namespace.
Apps that use lightning:container should work with data, not metadata. Don’t use the session key for your app to manage
custom objects or fields. You can use the session key to create and update object records.
Content in lightning:container is served from the Lightning container domain and is available in Lightning Experience and
the Salesforce mobile app. lightning:container can’t be used in Lightning pages that aren’t served from the Lightning domain,
such as Visualforce pages, Community Builder, or in external apps through Lightning Out.

SEE ALSO:
Lightning Container

The Lightning Realty App

The Lightning Realty App is a more robust example of messaging between the Lightning Container Component and Salesforce.
The Lightning realty app’s messaging framework relies on code in a Lightning component, the component’s handler, and the static
resource referenced by lightning:container. The Lightning container component points to the message handling function in
the Lightning component’s JavaScript controller. The message handling function takes in a message sent by the source JavaScript, which
uses a method provided by the lightning-container NPM module.
See Install the Example Lightning Realty App for instructions to install this example in your development org.
Let’s look at the Lightning component first. Although the code that defines the Realty component is simple, it allows the JavaScript of
the realty app to communicate with Salesforce and load sample data.
<aura:component access="global" implements="flexipage:availableForAllPageTypes" >

<aura:attribute access="global" name="mainTitle" type="String" required="true"

default="My Properties"/>

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Creating Apps The Lightning Realty App

<aura:attribute access="private" name="messageReceived" type="String" default=""/>

<aura:attribute access="private" name="error" type="String" default=""/>

<div>
<aura:if isTrue="{! !empty(v.messageReceived)}">
<lightning:textarea name="messageReceivedTextArea" value="{!v.messageReceived}"
label=" "/>
</aura:if>

<aura:if isTrue="{! !empty(v.error)}">

<lightning:textarea name="errorTextArea" value="{!v.error}" label="Error: "/>

</aura:if>

<lightning:container aura:id="ReactApp"
src="{!$Resource.Realty + '/index.html?mainTitle=' +
v.mainTitle}"
onmessage="{!c.handleMessage}"
onerror="{!c.handleError}"/>
</div>

</aura:component>

This code is similar to the example code in Sending Messages from the Lightning Container Component and Handling Errors in Your
Container.
There’s also code in the Lightning component’s controller and in the source JavaScript that allows the iframed app to communicate
with Salesforce. In PropertyHome.js, part of the source, the realty app calls LCC.sendMessage. This segment of code filters
the list of properties, then creates a message to send back to the container that includes the selected property’s address, price, city, state,
zip code, and description.
saveHandler(property) {
let filteredProperty = propertyService.filterProperty(property);
propertyService.createItem(filteredProperty).then(() => {
propertyService.findAll(this.state.sort).then(properties => {
let filteredProperties = propertyService.filterFoundProperties(properties);
this.setState({addingProperty: false, properties:filteredProperties});
});
let message = {};
message.address = property.address;
message.price = property.price;
message.city = property.city;
message.state = property.state;
message.zip = property.zip;
message.description = property.description;
LCC.sendMessage({name: "PropertyCreated", value: message});
});
},

Then, the JavaScript calls LCC.sendMessage with a name-value pair. This code uses the sendMessage method, which is part
of the messaging API provided by the lightning-container NPM module. For more information, see Sending Messages to the Lightning
Container Component.

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Creating Apps The Lightning Realty App

The last bit of action happens in the component’s controller, in the handleMessage() function.
handleMessage: function(component, message, helper) {
var payload = message.getParams().payload;
var name = payload.name;
if (name === "PropertyCreated") {
var value = payload.value;
var messageToUser;
if (value.price > 1000000) {
messageToUser = "Big Real Estate Opportunity in " + value.city + ", " +
value.state + " : $" + value.price;
}
else {
messageToUser = "Small Real Estate Opportunity in " + value.city + ", " +
value.state + " : $" + value.price;
}
var log = component.get("v.log");
log.push(messageToUser);
component.set("v.log", log);
}
},

This function takes a message as an argument, and checks that the name is "PropertyCreated". This is the same name set by
LCC.sendMessage in the app’s JavaScript.
This function takes the message payload—in this case, a JSON array describing a property—and checks the value of the property. If the
value is over $1 million, it sends a message to the user telling him or her that there’s a big real estate opportunity. Otherwise, it returns
a message telling the user that there’s a smaller real estate opportunity.

IN THIS SECTION:
Install the Example Lightning Realty App
See further examples of lightning:container in the Developerforce Git repository.

Install the Example Lightning Realty App

See further examples of lightning:container in the Developerforce Git repository.
Implement a more in-depth example of lightning:container with the code included in
https://github.com/developerforce/LightningContainerExamples. This example uses React and lightning:container to show
a real estate listing app in a Lightning page.
To implement this example, use npm. The easiest way to install npm is by installing node.js. Once you’ve installed npm, install the latest
version by running npm install --save latest-version from the command line.
To create custom Lightning components, you also need to have enabled My Domain in your org. For more information on My Domain,
see My Domain in the Salesforce Help.
1. Clone the Git repository. From the command line, enter git clone
https://github.com/developerforce/LightningContainerExamples
2. From the command line, navigate to LightningContainerExamples/ReactJS/Javascript/Realty and build
the project’s dependencies by entering npm install.
3. From the command line, build the app by entering npm run build.
4. Edit package.json and add your Salesforce login credentials where indicated.

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Creating Apps lightning-container NPM Module Reference

5. From the command line, enter npm run deploy.

6. Log in to Salesforce and activate the new Realty Lightning page in the Lightning App Builder by adding it to a Lightning app.
7. To upload sample data to your org, enter npm run load from the command line.
See the Lightning realty app in action in your org. The app uses lightning:container to embed a React app in a Lightning
page, displaying sample real estate listing data.

The component and handler code are similar to the examples in Sending Messages from the Lightning Container Component and
Handling Errors in Your Container.

lightning-container NPM Module Reference

Use methods included in the lightning-container NPM module in your JavaScript code to send and receive messages to and from your
custom Lightning component, and to interact with the Salesforce REST API.

IN THIS SECTION:
addMessageErrorHandler()
Mounts an error handling function, to be called when the messaging framework encounters an error.
addMessageHandler()
Mounts a message handling function, used to handle messages sent from the Lightning component to the framed JavaScript app.
callApex()
Makes an Apex call.

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getRESTAPISessionKey()
Returns the Salesforce REST API session key.
removeMessageErrorHandler()
Unmounts the error handling function.
removeMessageHandler()
Unmounts the message-handling function.
sendMessage()
Sends a message from the framed JavaScript code to the Lightning component.

addMessageErrorHandler()
Mounts an error handling function, to be called when the messaging framework encounters an error.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example mounts a
message error handling function. In a React app, functions must be mounted to be part of the document-object model and rendered
in the output.
componentDidMount() {
LCC.addMessageErrorHandler(this.onMessageError);
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

handler: (errorMsg: function The function that handles error messages encountered in
string) => void) the messaging framework.

Response
None.

addMessageHandler()
Mounts a message handling function, used to handle messages sent from the Lightning component to the framed JavaScript app.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example mounts a
message handling function. In a React app, functions must be mounted to be part of the document-object model and rendered in the
output.
componentDidMount() {
LCC.addMessageHandler(this.onMessage);

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onMessage(msg) {
let name = msg.name;
if (name === "General") {
let value = msg.value;
this.setState({messageReceived: value});
}
else if (name === "Foo") {
// A different response
}
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

handler: (userMsg: any) function The function that handles messages sent from the Lightning
=> void component.

Response
None.

callApex()
Makes an Apex call.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example calls the Apex
method getAccount.
callApex() {
LCC.callApex("lcc1.ApexController.getAccount",
this.state.name,
this.handleAccountQueryResponse,
{escape: true});
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

fullyQualifiedApexMethodName string The name of the Apex method.

apexMethodParameters array A JSON array of arguments for the Apex method.

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Name Type Description

callbackFunction function A callback function.

apexCallConfiguration array Configuration parameters for the Apex call.

Response
None.

getRESTAPISessionKey()
Returns the Salesforce REST API session key.
Use this method when your embedded app needs to interact with the Salesforce REST API, such as executing a SOQL query.
Don’t use the session key to manage custom objects or fields. You can use the session key to create and update object records. Apps
that use lightning:container should work with data, not metadata.

Important: It's important to keep your API key secure. Don't give this key to code you don't trust, and don't include it in URLs or
hyperlinks, even to another page in your app.
Salesforce uses the no-referrer policy to protect against leaking your app's URL to outside servers, such as image hosts. However,
this policy doesn't protect some browsers, meaning your app's URLs could be included in outside requests.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example gets the REST
API session key and uses it to execute a SOQL query.
componentDidMount() {
let sid = LCC.getRESTAPISessionKey();
let conn = new JSForce.Connection({accessToken: sid});
conn.query("SELECT Id, Name from Account LIMIT 50", this.handleAccountQueryResponse);
}

You can view and download this example in the Developerforce Github Repository.

Arguments
None.

Response

Name Type Description

key string The REST API session key.

removeMessageErrorHandler()
Unmounts the error handling function.

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When using React, it’s necessary to unmount functions to remove them from the DOM and perform necessary cleanup.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example unmounts a
message error handling function. In a React app, functions must be mounted to be part of the document-object model and rendered
in the output.
componentWillUnmount() {
LCC.removeMessageErrorHandler(this.onMessageError);
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

handler: (errorMsg: function The function that handles error messages encountered in
string) => void) the messaging framework.

Response
None.

removeMessageHandler()
Unmounts the message-handling function.
When using React, it’s necessary to unmount functions to remove them from the DOM and perform necessary cleanup.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example unmounts a
message handling function.
componentWillUnmount() {
LCC.removeMessageHandler(this.onMessage);
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

handler: (userMsg: any) function The function that handles messages sent from the Lightning
=> void component.

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Creating Apps Controlling Access

Response
None.

sendMessage()
Sends a message from the framed JavaScript code to the Lightning component.

Sample
Used within a JavaScript app uploaded as a static resource and referenced by lightning:container, this example sends a
message from the app to lightning:container.
sendMessage() {
LCC.sendMessage({name: "General", value: this.state.messageToSend});
}

You can view and download this example in the Developerforce Github Repository.

Arguments

Name Type Description

userMsg any While the data sent in the message is entirely under your
control, by convention it’s an object with name and value
fields.

Response
None.

Controlling Access
The framework enables you to control access to your applications, attributes, components, events, interfaces, and methods via the
access system attribute. The access system attribute indicates whether the file can be used outside of its own namespace.
Use the access system attribute on these tags:
• <aura:application>
• <aura:attribute>
• <aura:component>
• <aura:event>
• <aura:interface>
• <aura:method>

Access Values
You can specify these values for the access system attribute.

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Creating Apps Controlling Access

Note: If you’re an internal Salesforce developer, look at our internal doc as access levels work differently than they do for open-source
implementations.
private
Available within the component, app, interface, event, or method and can’t be referenced outside the file. This value can only be
used for <aura:attribute> or <aura:method>.
Marking an attribute as private makes it easier to refactor the attribute in the future as the attribute can only be used within the file.
Accessing a private attribute returns undefined unless you reference it from the component in which it’s declared. You can’t
access a private attribute from a sub-component that extends the component containing the private attribute.
public
Available within the same namespace.
internal
Available within any internal namespace. An internal namespace is a namespace loaded from the filesystem. This is the default access
value.
Resources, such as components, in an internal namespace may access global, internal, public (in the same namespace),
or private (in the same component) resources.
global
Available in all namespaces.

Example
This sample component has global access.
<aura:component access="global">
...
</aura:component>

Access Violations
If your code accesses a resource, such as a component, that doesn’t have an access system attribute allowing you to access the
resource:
• Client-side code doesn’t execute or returns undefined. You also see an error message in your browser console unless you’re
running in PROD mode.
• Server-side code results in the component failing to load. You also see a popup error message unless you’re running in PROD mode.

Anatomy of an Access Check Error Message

Here is a sample access check error message for an access violation.
Access Check Failed ! ComponentService.getDef():'markup://c:targetComponent' is not
visible to 'markup://c:sourceComponent'.

An error message has four parts:

1. The context (who is trying to access the resource). In our example, this is markup://c:sourceComponent.
2. The target (the resource being accessed). In our example, this is markup://c:targetComponent.
3. The type of failure. In our example, this is not visible.

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4. The code that triggered the failure. This is usually a class method. In our example, this is ComponentService.getDef(),
which means that the target definition (component) was not accessible. A definition describes metadata for a resource, such as a
component.

Fixing Access Check Errors

You can fix access check errors using one or more of these techniques.
• Add appropriate access system attributes to the resources that you own.
• Remove references in your code to resources that aren’t available. In the earlier example, markup://c:targetComponent
doesn’t have an access value allowing markup://c:sourceComponent to access it.
• Ensure that an attribute that you’re accessing exists by looking at its <aura:attribute> definition. Confirm that you’re using
the correct case-sensitive spelling for the name.
Accessing an undefined attribute or an attribute that is out of scope, for example a private attribute, triggers the same access violation
message. The access context doesn’t know whether the attribute is undefined or inaccessible.

Example: is not visible to 'undefined'

ComponentService.getDef():'markup://c:targetComponent' is not visible to 'undefined'

The key word in this error message is undefined, which indicates that the framework has lost context. This happens when your code
accesses a component outside the normal framework lifecycle, such as in a setTimeout() or setInterval() call or in an ES6
Promise.
Fix this error by wrapping the code in a $A.getCallback() call. For more information, see Modifying Components Outside the
Framework Lifecycle.

Example: Cannot read property 'Yb' of undefined

Action failed: c$sourceComponent$controller$doInit [Cannot read property 'Yb' of undefined]

This error message happens when you reference a property on a variable with a value of undefined. The error can happen in many
contexts, one of which is the side-effect of an access check failure. For example, let’s see what happens when you try to access an
undefined attribute, imaginaryAttribute, in JavaScript.
var whatDoYouExpect = cmp.get("v.imaginaryAttribute");

This is an access check error and whatDoYouExpect is set to undefined. Now, if you try to access a property on
whatDoYouExpect, you get an error.

Action failed: c$sourceComponent$controller$doInit [Cannot read property 'Yb' of undefined]

The c$sourceComponent$controller$doInit portion of the error message tells you that the error is in the doInit
method of the controller of the sourceComponent component in the c namespace.

IN THIS SECTION:
Application Access Control
The access attribute on the aura:application tag controls whether the app can be used outside of the app’s namespace.

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Creating Apps Application Access Control

Interface Access Control

The access attribute on the aura:interface tag controls whether the interface can be used outside of the interface’s
namespace.
Component Access Control
The access attribute on the aura:component tag controls whether the component can be used outside of the component’s
namespace.
Attribute Access Control
The access attribute on the aura:attribute tag controls whether the attribute can be used outside of the attribute’s
namespace.
Event Access Control
The access attribute on the aura:event tag controls whether the event can be used outside of the event’s namespace.

Application Access Control

The access attribute on the aura:application tag controls whether the app can be used outside of the app’s namespace.
Possible values are listed below.

Modifier Description
public Available within the same namespace.

internal Available within any internal namespace. An internal namespace is a namespace loaded from the
filesystem. This is the default access value. If set to internal, the app isn’t directly accessible via
a URL in PROD mode.

global Available in all namespaces.

Interface Access Control

The access attribute on the aura:interface tag controls whether the interface can be used outside of the interface’s namespace.
Possible values are listed below.

Modifier Description
public Available within the same namespace.

internal Available within any internal namespace. An internal namespace is a namespace loaded from the
filesystem. This is the default access value.

global Available in all namespaces.

An interface can extend another interface but a component can’t extend an interface. A component can implement an interface using
the implements attribute on the aura:component tag.

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Component Access Control

The access attribute on the aura:component tag controls whether the component can be used outside of the component’s
namespace.
Possible values are listed below.

Modifier Description
public Available within the same namespace.

internal Available within any internal namespace. An internal namespace is a namespace loaded from the
filesystem. This is the default access value. If set to internal, the component isn’t directly accessible
via a URL in PROD mode.

global Available in all namespaces.

Attribute Access Control

The access attribute on the aura:attribute tag controls whether the attribute can be used outside of the attribute’s namespace.
Possible values are listed below.

Access Description
private Available within the component, app, interface, event, or method and can’t be referenced outside
the file.

Note: Accessing a private attribute returns undefined unless you reference it from the
component in which it’s declared. You can’t access a private attribute from a sub-component
that extends the component containing the private attribute.

public Available within the same namespace.

internal Available within any internal namespace. An internal namespace is a namespace loaded from the
filesystem. This is the default access value.

global Available in all namespaces.

Event Access Control

The access attribute on the aura:event tag controls whether the event can be used outside of the event’s namespace.
Possible values are listed below.

Modifier Description
public Available within the same namespace.

internal Available within any internal namespace. An internal namespace is a namespace loaded from the
filesystem. This is the default access value.

global Available in all namespaces.

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Creating Apps URL-Centric Navigation

URL-Centric Navigation
It's useful to understand how the framework handles page requests. The initial GET request for an app retrieves a template containing
all the framework JavaScript and a skeletal HTML response. All subsequent changes to everything after the # in the URL trigger an
XMLHttpRequest (XHR) request for the content. The client service makes the request, and returns the result to the browser.
The portion of the URL before the # value doesn't change after the initial app request. The app is long-lived with subsequent actions
causing incremental changes to the DOM for the lifetime of the app.

Navigation Events
The framework uses its event model to manage content change in response to URL changes. The framework monitors the location of
the current window for changes. If the # value in a URL changes, the framework fires an application event of type
aura:locationChange. The locationChange event has a single attribute called token.
For example, if the URL changes from /demo/test.app# to /demo/test.app#foo, a aura:locationChange event
is fired, and the token attribute on that event is set to foo.

IN THIS SECTION:
Using Custom Events in URL-Centric Navigation
Accessing Tokenized Event Attributes

SEE ALSO:
Modes Reference
aura:application
Initial Application Request

Using Custom Events in URL-Centric Navigation

If your application requires a more complex URL schema, with name-value pairs that you want to tokenize, you can extend
aura:locationChange to add your own event type. For example, you could create the
demo/myLocationChange/myLocationChange.evt event so that the framework automatically parses the thing1 and
thing2 attributes in the URL.

<aura:event type="application" extends="aura:locationChange">

<aura:attribute name="thing1" type="String"/>
<aura:attribute name="thing2" type="Boolean"/>
</aura:event>

Update the locationChangeEvent attribute in your <aura:application> component to indicate to the framework that
you want to parse the hash of the URL into the custom event.
<aura:application locationChangeEvent="demo:myLocationChange">

Now, when the URL changes to /demo/test.app#foo?thing1=Howdy&thing2=true, the framework fires an event of
type demo:myLocationChange with token set to foo, thing1 set to Howdy and thing2 set to true.

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Creating Apps Accessing Tokenized Event Attributes

Note: The attributes after the # value use the same format as a query string: #foo?thing1=Howdy&thing2=true.
However, a real request query string starts before the # value. A sample query string that sets the mode to PROD (production)
is /demo/test.app?aura.mode=PROD&queryStrParam2=val2#foo.

Accessing Tokenized Event Attributes

To see how you'd access the tokenized attributes, imagine a scenario where a component uses a getHomeComponents server-side
action to retrieve components. You can write the getHomeComponents action to accept arguments that match the attributes in
your custom location change event. The arguments are automatically mapped from the location change event to the action call.
@AuraEnabled
public static Aura.Component[] getHomeComponents(String token, String thing1, Boolean
thing2){...}

Using Object-Oriented Development

The framework provides the basic constructs of inheritance and encapsulation from object-oriented programming and applies them to
presentation layer development.
For example, components are encapsulated and their internals stay private. Consumers of the component can access the public shape
(attributes and registered events) of the component, but can't access other implementation details in the component bundle. This strong
separation gives component authors freedom to change the internal implementation details and insulates component consumers from
those changes.
You can extend a component, app, interface or an event, or you can implement a component interface.

What is Inherited?
This topic lists what is inherited when you extend a definition, such as a component.
When a component contains another component, we refer in the documentation to parent and child components in the containment
hierarchy. When a component extends another component, we refer to sub and super components in the inheritance hierarchy.

Component Attributes
A sub component that extends a super component inherits the attributes of the super component. Use <aura:set> in the markup
of a sub component to set the value of an attribute inherited from a super component.

Events
A sub component that extends a super component can handle events fired by the super component. The sub component automatically
inherits the event handlers from the super component.
The super and sub component can handle the same event in different ways by adding an <aura:handler> tag to the sub component.
The framework doesn't guarantee the order of event handling.
When an event fires, handlers for the event are executed. Handlers for any event that extend the event are also executed.

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Creating Apps Inherited Component Attributes

Helpers
A sub component's helper inherits the methods from the helper of its super component. A sub component can override a super
component's helper method by defining a method with the same name as an inherited method.

Controllers
A sub component that extends a super component can call actions in the super component's client-side controller. For example, if the
super component has an action called doSomething, the sub component can directly call the action using the {!c.doSomething}
syntax.

Note: We don't recommend using inheritance of client-side controllers as this feature may be deprecated in the future to preserve
better component encapsulation. We recommend that you put common code in a helper instead.

Models Are Not Inherited

A component's model is not inherited by a component that extends a super component.

SEE ALSO:
Component Attributes
Communicating with Events
Sharing JavaScript Code in a Component Bundle
Handling Events with Client-Side Controllers
aura:set
Java Models

Inherited Component Attributes

A sub component that extends a super component inherits the attributes of the super component.
Attribute values are identical at any level of extension. There is an exception to this rule for the body attribute, which we'll look at more
closely soon.
Let's start with a simple example. c:super has a description attribute with a value of "Default description",
<!--c:super-->
<aura:component extensible="true">
<aura:attribute name="description" type="String" default="Default description" />

<p>super.cmp description: {!v.description}</p>

{!v.body}
</aura:component>

Don’t worry about the {!v.body} expression for now. We’ll explain that when we talk about the body attribute.
c:sub extends c:super by setting extends="c:super" in its <aura:component> tag.

<!--c:sub-->
<aura:component extends="c:super">
<p>sub.cmp description: {!v.description}</p>
</aura:component

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Creating Apps Inherited Component Attributes

Note that sub.cmp has access to the inherited description attribute and it has the same value in sub.cmp and super.cmp.
Use <aura:set> in the markup of a sub component to set the value of an inherited attribute.

Inherited body Attribute

Every component inherits the body attribute from <aura:component>. The inheritance behavior of body is different than other
attributes. It can have different values at each level of component extension to enable different output from each component in the
inheritance chain. This will be clearer when we look at an example.
Any free markup that is not enclosed in another tag is assumed to be part of the body. It's equivalent to wrapping that free markup
inside <aura:set attribute="body">.
The default renderer for a component iterates through its body attribute, renders everything, and passes the rendered data to its super
component. The super component can output the data passed to it by including {!v.body} in its markup. If there is no super
component, you've hit the root component and the data is inserted into document.body.
Let's look at a simple example to understand how the body attribute behaves at different levels of component extension. We have
three components.
c:superBody is the super component. It inherently extends <aura:component>.

<!--c:superBody-->
<aura:component extensible="true">
Parent body: {!v.body}
</aura:component>

At this point, c:superBody doesn’t output anything for {!v.body} as it’s just a placeholder for data that will be passed in by a
component that extends c:superBody.
c:subBody extends c:superBody by setting extends="c:superBody" in its <aura:component> tag.

<!--c:subBody-->
<aura:component extends="c:superBody">
Child body: {!v.body}
</aura:component>

c:subBody outputs:

Parent body: Child body:

In other words, c:subBody sets the value for {!v.body} in its super component, c:superBody.
c:containerBody contains a reference to c:subBody.

<!--c:containerBody-->
<aura:component>
<c:subBody>
Body value
</c:subBody>
</aura:component>

In c:containerBody, we set the body attribute of c:subBody to Body value. c:containerBody outputs:
Parent body: Child body: Body value

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Creating Apps Abstract Components

SEE ALSO:
aura:set
Component Body
Component Markup

Abstract Components
Object-oriented languages, such as Java, support the concept of an abstract class that provides a partial implementation for an object
but leaves the remaining implementation to concrete sub-classes. An abstract class in Java can't be instantiated directly, but a non-abstract
subclass can.
Similarly, Aura supports the concept of abstract components that have a partial implementation but leave the remaining implementation
to concrete sub-components.
To use an abstract component, you must either extend it and fill out the remaining implementation, or add a provider. An abstract
component can't be used directly in markup unless you define a provider.
The <aura:component> tag has a boolean abstract attribute. Set abstract="true" to make the component abstract.

SEE ALSO:
Server-Side Runtime Binding of Components
Interfaces

Interfaces
Object-oriented languages, such as Java, support the concept of an interface that defines a set of method signatures. A class that
implements the interface must provide the method implementations. An interface in Java can't be instantiated directly, but a class that
implements the interface can.
Similarly, Aura supports the concept of interfaces that define a component's shape by defining its attributes.
An interface starts with the <aura:interface> tag. It can only contain these tags:
• <aura:attribute> tags to define the interface's attributes.
• <aura:registerEvent> tags to define the events that it may fire.
You can't use markup, renderers, controllers, models, or anything else in an interface.
To use an interface, you must implement it. An interface can't be used directly in markup otherwise. Set the implements system
attribute in the <aura:component> tag to the name of the interface that you are implementing. For example:
<aura:component implements="mynamespace:myinterface" >

A component can implement an interface and extend another component.

<aura:component extends="ns1:cmp1" implements="ns2:intf1" >

An interface can extend multiple interfaces using a comma-separated list.

<aura:interface extends="ns:intf1,ns:int2" >

Note: Use <aura:set> in a sub component to set the value of any attribute that is inherited from the super component. This
usage works for components and abstract components, but it doesn't work for interfaces. To set the value of an attribute inherited

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Creating Apps Inheritance Rules

from an interface, redefine the attribute in the sub component using <aura:attribute> and set the value in its default
attribute.
Since there are fewer restrictions on the content of abstract components, they are more common than interfaces. A component can
implement multiple interfaces but can only extend one abstract component, so interfaces can be more useful for some design patterns.

SEE ALSO:
Server-Side Runtime Binding of Components
Setting Attributes Inherited from an Interface
Abstract Components

Marker Interfaces
You can use an interface as a marker interface that is implemented by a set of components that you want to easily identify for specific
usage in your app.
In JavaScript, you can determine if a component implements an interface by using
myCmp.isInstanceOf("mynamespace:myinterface").
In Java, use the isInstanceOf() method in the ComponentDef or ApplicationDef interfaces.

Inheritance Rules
This table describes the inheritance rules for various elements.

Element extends implements Default Base Element

component one extensible component multiple interfaces <aura:component>

app one extensible app N/A <aura:application>

interface multiple interfaces using a comma-separated list N/A N/A

(extends="ns:intf1,ns:int2")

component event one component event N/A <aura:componentEvent>

application event one application event N/A <aura:applicationEvent>

SEE ALSO:
Interfaces
Communicating with Events

Caching with Storage Service

The Storage Service provides a powerful, simple-to-use caching infrastructure that enhances the user experience on the client. Client
applications can benefit from caching data to reduce response times of pages by storing and accessing data locally rather than requesting
data from the server. Caching is especially beneficial for high-performance, mostly connected applications operating over high latency
connections, such as 3G networks.
The storage name is required and must be unique.

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There are two types of storage:

• Storable actions: Storable actions cache server action response values. The storage name must be actions.
• Custom named storage: Storage that you control by adding and retrieving items to and from storage. The storage name can be any
name except for actions, which is reserved for caching action response values.

SEE ALSO:
Creating Server-Side Logic with Controllers
Storable Actions
Initializing Storage Service

Storage Service Adapters

The Storage Service supports multiple implementations of storage and selects an adapter at runtime based on browser support and
specified characteristics of persistence and security. Storage can be persistent and secure. With persistent storage, cached data is preserved
between user sessions in the browser. With secure storage, cached data is encrypted.

Storage Adapter Name Persistent Secure

IndexedDB true false

Memory false true

IndexedDB
(Persistent but not secure) Provides access to an API for client-side storage and search of structured data. For more information, see
the Indexed Database API.
Memory
(Not persistent but secure) Provides access to JavaScript memory for caching data. The stored cache persists only per browser page.
Browsing to a new page resets the cache.
The Storage Service selects a storage adapter on your behalf that matches the persistent and secure options you specify when initializing
the service. For example, if you request a persistent and insecure storage service, the Storage Service returns the IndexedDB storage if
the browser supports it.

SEE ALSO:
Initializing Storage Service

Initializing Storage Service

Initialize storage in markup or JavaScript by specifying a name and, optionally, other properties.
If you don't specify the optional properties, the Storage Service uses default values set by the initStorage() method of
AuraStorageService.

Storage Entry Expiration

When you initialize storage, you can configure the expiration time, which is the duration in seconds that an entry is retained in storage.
To set the expiration time in markup, use the defaultExpiration attribute in <auraStorage:init>.

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To set the expiration time in JavaScript, use the expiration property in $A.storageService.initStorage(config).

Storage Entry Refresh Interval

When you initialize storage, you can configure the refresh interval, which is the duration in seconds before an entry is refreshed in storage.
If an action matches a storage entry, the callback in the client-side controller is invoked for the cached action response.
If the response has been cached for longer than the refresh interval, the storage entry is refreshed. If the refreshed response is different
from the cached response, the callback in the client-side controller is executed for a second time.
To set the refresh interval in markup, use the defaultAutoRefreshInterval attribute in <auraStorage:init>.
To set the refresh interval in JavaScript, use the autoRefreshInterval property in
$A.storageService.initStorage(config).

Initialize in Markup
This example uses a template to initialize storage for server-side action response values. The template contains an
<auraStorage:init> tag that specifies storage initialization properties.

<aura:component isTemplate="true" extends="aura:template">

<aura:set attribute="auraPreInitBlock">
<auraStorage:init
name="actions"
persistent="false"
secure="true"
maxSize="1024"
defaultExpiration="900"
defaultAutoRefreshInterval="30" />
</aura:set>
</aura:component>

name
The name for the storage instance.
persistent
Set to true to preserve cached data between user sessions in the browser.
secure
Set to true to encrypt cached data.
maxsize
The maximum size in KB of the storage.
defaultExpiration
The duration in seconds that an entry is retained in storage.
defaultAutoRefreshInterval
The duration in seconds before an entry is refreshed in storage.

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Initialize in JavaScript
Initialize storage dynamically using the JavaScript API. This example shows how to initialize the Storage Service using
initStorage(config) in a JavaScript client-side controller.

var storage = $A.storageService.initStorage({

"name": "MyStorage",
"persistent": true,
"secure": true,
"maxSize": 524288, // (bytes) (512 * 1024)
"expiration": 900, // (seconds)
"autoRefreshInterval": 30, // (seconds)
"debugLogging": true,
"clearOnInit": false,
"version": "1.0"
});

Warning: The maxSize property in $A.storageService.initStorage() has a unit of bytes. This is different than
the maxSize attribute in <auraStorage:init>, which has a unit of KB.

Storage Versions
The storage service uses an optional version as part of the key when getting or setting items. This attribute enables you to cache data
specific to different versions of your app. You can change the default version for an app. When you retrieve data from the cache using
the new version, the cached data for the old version is ignored as it has a different key. This avoids the problem of clients retrieving data
associated with an old version from the cache.
There are two types of versions for storage: an app-level default version and a version specific to an individual store. If you don't specify
a version when you create storage, the storage inherits the app-level default.
Use $A.storageService.setVersion() to create an app-level version. Use the version parameter in
$A.storageService.initStorage() or the version attribute in <auraStorage:init> to set a storage-specific
version when you initialize the storage.

SEE ALSO:
Storable Actions
Using Storage Service

Using Storage Service

After you've initialized your custom storage, you can add and retrieve items from your storage. To do so, use the JavaScript set and
get API of AuraStorage.
Storage Service uses ES6 Promises. For more information about promises, see
https://developers.google.com/web/fundamentals/getting-started/primers/promises.
AuraStorage calls are asynchronous and return a Promise object that is resolved when the operation completes, or rejected if
an error occurred.

Note: Promises execute their resolve and reject functions asynchronously so the code is outside the Aura event loop and normal
rendering lifecycle. If the resolve or reject code makes any calls to Aura, such as setting a component attribute, use
$A.getCallback() to wrap the code. For more information, see Modifying Components Outside the Framework Lifecycle
on page 169.

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The framework-provided actions storage for server-side actions automatically adds and retrieves items from storage and doesn't require
you to call set and get explicitly. See Storable Actions on page 208.

Getting and Setting Items

This example shows how to use a storage object to explicitly store items. For information on initializing a storage object, see Initializing
Storage Service on page 245.
The call to set takes a key that is used to uniquely identify the stored item, and returns a Promise that resolves when the operation
is complete.
var value1 = 67;
// returns a Promise object that is not used here
storage.set("score", value1);

storage.set("name", "joe smith")

.then(function() { console.log("name is stored"); },
function(err) { console.log("named failed to store: " + err) }
);

The first function in then() is called when the Promise resolves. The second function is called when the Promise rejects.
You can retrieve stored items by using the get method. The get method takes as a parameter the key of the object you wish to
retrieve. It returns a Promise that resolves to the retrieved value or undefined if the key is not found.
storage.get("score")
.then(function(value) { console.log("score is " + value); })
.then(function() { return storage.get("name"); })
.then(function(value) { console.log("name is " + value); },
function(err) { console.log("failed: " + err); }
);

Note: If you’re getting or setting more than one value, use getAll() or setAll() for better performance.

Using Other AuraStorage Methods

You can obtain any initialized named storage by calling getStorage() and by passing it the storage name. For example:
var storage = $A.storageService.getStorage("MyStorage");

Note: The getName() method returns the type of storage selected, not the name of the storage.

There are other methods available in the JavaScript API. For example, you can get the current and max size:
var storage = $A.storageService.getStorage("MyStorage");
storage.getSize().then(
function(size) { return size; },
function(err) { return "unknown"; }
).then(function(size) {
var max = storage.getMaxSize();
console.log("size is " + size + " KB of max " + max + " KB");
});

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Creating Apps Using the AppCache

To clear the storage:

var storage = $A.storageService.getStorage("MyStorage";
storage.clear().then(
function() { console.log("storage has cleared"); },
function(err) { console.log("storage failed to clear: " + err); }
);

SEE ALSO:
Storable Actions
Initializing Storage Service

Using the AppCache

AppCache support is deprecated. Browser vendors have deprecated AppCache, so we followed their lead. Remove the useAppcache
attribute in the <aura:application> tag of your standalone apps (.app files) to avoid cross-browser support issues due to
deprecation by browser vendors.
If you don’t currently set useAppcache in an <aura:application> tag, you don’t have to do anything because the default
value of useAppcache is false.

Note: See an introduction to AppCache for more information.

SEE ALSO:
Component Request Overview
aura:application

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TESTING AND DEBUGGING

CHAPTER 6 Testing and Debugging Components

In this chapter ... Aura's loosely coupled components facilitate maintainability and enable efficient testing. Components
are isolated from their application context for easier testing. Aura supports JavaScript testing for
• JavaScript Test Suite components and applications in production mode.
Setup
Add component tests to a JavaScript file in the component bundle. For example, a component
• Assertions
myData.cmp in the myApp namespace is saved in the folder myData, which can contain a test
• Debugging file myDataTest.js.
Components
To reuse code among test cases, use the setUp and tearDown functions, which can be useful for
• Utility Functions
quickly setting up or removing objects. They are called before and after a test method is run. During test
• Sample Test Cases execution, additional suite methods can be accessed with this.sharedMethod().
• Mocking Java
Classes Note: You can view Aura's test methods in the JavaScript API reference. Assertions and utility
functions are also available for unit testing.
Run JavaScript tests in a Web browser by appending ?aura.mode=JSTEST to your production
component. For example, if you have a component myData.cmp in the myApp namespace, you
can run test cases on http://<your server>/myApp/myData.cmp?aura.mode=JSTEST.

SEE ALSO:
Component Bundles
Modes Reference
Assertions
Utility Functions

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Testing and Debugging Components JavaScript Test Suite Setup

JavaScript Test Suite Setup

A test file in a component bundle contains a suite of tests and properties, where each function represents a different test case.
You would typically define any shared properties before your test cases. Your test functions must follow the naming convention
test<testName>. Prepending an underscore to the test function name like _testGetResult disables the test. A basic test
suite looks like this.
({
/** Properties shared across test cases**/
attributes: {
label: 'Submit',
//Other attributes here
},
browsers: ['GOOGLECHROME', 'SAFARI', 'IPAD' ],
setUp: function(component){
//Runs before each test case is executed but after component initialization
},
tearDown: function(component){
//Runs after each test case is executed
},
sharedMethod: function(arg1, arg2){
//Utility functions that are invoked by calling this.sharedMethod(x, y)
},

/** Test Cases **/

testCase1: {
attributes: {
//Attributes
},
//Runs all supported browsers except Firefox.
//Overrides the suite level browsers tag.
browsers: [ '-FIREFOX'],
test: [ //A single function or a list of functions
function(component){
//Test something
},
function(component){
//Test something
}
]
}
})

The attributes property specifies the attribute values that the component to be tested should be instantiated with. The
attributes and browsers properties are optional.

Test Suite Properties

Test suite properties are values that the target component are instantiated with. The following lists supported properties for a test suite.
attributes
Applies to suite or test level. Setting attribute values outside of a test case applies the attribute values to the whole suite. If a test has
both test level and suite level attributes, the test level attributes override those at the suite level.

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Testing and Debugging Components JavaScript Test Suite Setup

Attribute values are passed as query parameters in the initial GET request. For example, this code initializes the label and
buttonTitle attributes on a ui:button component.

attributes:{
label: 'Submit',
buttonTitle: 'click once'
}

auraWarningsExpectedDuringInit
Applies to test level only and accepts an array of Strings, where each String is an expected warning message. When the
failOnWarning flag is set, auraWarningsExpectedDuringInit specify warnings from $A.warning allowed
during initialization that won’t fail the test. For more information, see Fail a Test Only When Expected on page 254.
browsers
Applies to suite or test level. List browsers you want all test cases to test against. If this property is not specified, the tests execute in
all supported browsers. Values prefixed with a hyphen exclude that browser from the test.
browsers: [ 'GOOGLECHROME', 'SAFARI', '-IPAD' ]

By default, the tests run on desktop and mobile browsers. To test only for desktop or mobile browsers, specify the DESKTOP or
MOBILE attribute.

browsers: [ 'DESKTOP'] // Run tests for desktop browsers only

If the browsers property is available in both the case level and the suite level, the case level property overrides the latter. Desktop
browsers include IE9, IE10, IE11, FIREFOX, GOOGLECHROME, and SAFARI. Mobile browsers include IPHONE, IPAD,
ANDROID_PHONE, ANDROID_TABLET.
doNotWrapInAuraRun
Applies to suite or test level. Each function block within a test is referred to as a stage. By default, each stage of the test executes
within its own $A.run() function to ensure the test code goes through the full rendering lifecycle and that all enqueued actions are
run before continuing on to the next stage or completing the test. If this is not the desired behavior for your tests, set
doNotWrapInAuraRun to true.
failOnWarning
Applies to suite or test level. If true, the test will fail on any warnings received during test execution not marked as expected via a
call to $A.test.expectWarnings(), or any warnings received during test setup not declared under the
auraWarningsExpectedDuringInit tag. For more information, see Fail a Test Only When Expected on page 254.
setUp
This property executes before each test case but after the component has been initialized.
tearDown
This property executes after each test case, regardless of the test status.
sharedMethod
Put additional utility functions here if your test needs to access them. This example is invoked with this.sharedMethod(x,y).
sharedMethod: function(argument1, argument2){
$A.test.assertNotNull(argument1, 'The first argument received was null');
}

sharedString
Share a string or function for multiple tests in the same test file.
sharedString: "My shared string",
sharedFunction: function(){},

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Testing and Debugging Components JavaScript Test Suite Setup

testFunction:function(){
this.sharedFunction(this.sharedString);
}

mocks
Mocking isolates your JavaScript tests from other resources, such as a Java model, provider, or server-side controller. Mocks that are
defined as a suite property are shared among all test cases. For more information, see Mocking Java Classes on page 285.

Test Cases
Test cases are typically defined after the suite properties. They contain the attributes, browsers, and mocks properties. If
these properties are specified in a test case, their values override those provided by suite properties. Additionally, a test case can contain
a test property that’s defined with a function or a list of functions. After the first function runs, the test waits for
$A.test.addWaitFor to complete. This example method compares expected and the return value of the
lookForTextAfterClick. When this comparison evaluates to true, the next function is run.

test: [
function(component){
$A.test.assertTrue(true, 'This obviously should have passed.');
$A.test.assertEquals( 'Opt Out', component.get("v.label"), "Wrong label.");
$A.test.assertEquals( 'click once', component.get("v.buttonTitle"), "Wrong
tooltip.");
debugger; // Break at this point in browsers that support the directive
component.get('e.press').fire();
$A.test.addWaitFor('expected', function(){
var lookForTextAfterClick = component.get('v.updatedOnClick');
return lookForTextAfterClick;
});
}, function(component){
$A.test.assertTrue(true, 'This also obviously should have passed after the click.');
}]

To display an error message when the test function times out, use $A.test.addWaitForWithFailureMessage. This example
runs a test that expects a result length of one by default, or two if the component is rendered on a phone.
test: function(cmp) {
var expectedResultLength = 1;
if ($A.get("$Browser.formFactor") == 'PHONE') {
expectedResultLength = 2;
}
$A.test.addWaitForWithFailureMessage(
expectedResultLength,
function() {
return result.length;
},
"Unexpected number of items in result");
}

IN THIS SECTION:
Pass a Controller Action in Component Tests
Invoke a controller action by wrapping it in a component.

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Testing and Debugging Components Pass a Controller Action in Component Tests

Fail a Test Only When Expected

You can set a test to expect an error or warning, and fail a test only when you expect it to fail.

Pass a Controller Action in Component Tests

Invoke a controller action by wrapping it in a component.
You can’t pass in a function or action as an attribute in component tests. Instead, use a component wrapper. For example, you want to
pass an action in the following component to a test.
<!-- myNamespace:childCmp -->
<aura:component>
<aura:attribute name="put" type="Aura.Action"/>
</aura:component>

Use a component wrapper that looks like this:

<aura:component>
<aura:attribute name="items" type="integer" default="0"/>
box called {!v.items} times
<myNamespace:childCmp aura:id="putter" put="{!c.box}"/>
</aura:component>

The controller action retrieves the items attribute in the component and increments its value.
({
box: function(cmp, event) {
var items = cmp.get("v.items");
cmp.set("v.items", items + 1);
}
})

The following test verifies the type of action that’s passed in the component. auraType checks if the object is of a certain type, for
example, whether it’s of type Component, Action, or Event.
testAction: {
test: function(component){
var box = component.get("c.box");
$A.test.assertAuraType("Action", box, "The type was incorrect.");
$A.test.assertEquals("function", typeof box.run, "The run was not a function on
the actions.");
}
}

Note: The auraType attribute is deprecated. Use $A.test.assertAuraType to check if a value is an instance of the
expected type.

Fail a Test Only When Expected

You can set a test to expect an error or warning, and fail a test only when you expect it to fail.
All tests will fail on errors by default. There is no tag/setting to make a test not fail on errors. You must mark each individual error as
expected. All tests will pass on warnings by default. If failOnWarning: true is set, then the test will fail for any warnings not
marked as expected.

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Testing and Debugging Components Assertions

To enable your test to expect an error or warning during initialization, use auraErrorsExpectedDuringInit or
auraWarningsExpectedDuringInit. The test fails only if any of the expected errors don’t happen. To enable your test to
expect an error or warning during the test itself, use $A.test.expectAuraError or $A.test.expectAuraWarning.
({
failOnWarning: true,

/**
* This case inherits the suite level failOnWarning so we need to declare
auraWarningsExpectedDuringInit to account
* for warning in the controller's init function and have $A.test.expectAuraWarning
for any warnings in the test
* block itself.
*/
testExpectedWarning: {
auraWarningsExpectedDuringInit: ["Expected warning from auraWarningTestController
init"],
test: function(cmp) {
var warningMsg = "Expected warning from testExpectedWarning";
var warningMsg2 = "Expected warning from testExpectedWarning2";
$A.test.expectAuraWarning(warningMsg);
$A.test.expectAuraWarning(warningMsg2);
$A.warning(warningMsg);
$A.warning(warningMsg2);
}
},

/**
* Override suite level failOnWarning and verify test does not fail on warnings.
*/
testNoFailOnWarning: {
failOnWarning: false,
test: function(cmp) {
$A.warning("Expected warning from testNoFailOnWarning");
}
}
})

Assertions
Assertions evaluate an object or expression for expected results and are the foundation of component testing. Each JavaScript test can
contain one or more assertions. The test passes only when all the assertions are successful. Assertions should be prefixed with $A.test.
If an assertion fails, an error message is typically returned with the assertMessage or errorMessage string.
Include unique and specific error messages in your assert statements. For example, use assertTrue(run, "Returns true
if the action has run successfully.") instead of a generic message. Making each assert message unique also
helps in narrowing down which assert statement has failed.
Aura supports the following assertions.

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Testing and Debugging Components Assertions

$A.test.assert()
Asserts that the condition is true.
Syntax

$A.test.assert(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The condition to evaluate.

assertMessage String The message that is returned if the condition is not false.

$A.test.assertAccessible()
Asserts that the HTML output of the target component is accessibility compliant. Throws an error containing a concatenated string
representation of all accessibility errors found.
Syntax
$A.test.assertAccessible()

$A.test.assert()
Asserts that the condition is true.
Syntax

$A.test.assert(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The condition to evaluate.

assertMessage String The message that is returned if the condition is not false.

$A.test.assertAuraType()
Asserts that the value is an instance of the expected type.
Syntax

$A.test.assertAuraType(type:String, condition:Object, assertMessage:String)

Arguments

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Testing and Debugging Components Assertions

Name Type Description

type String The type to evaluate. Valid types:
• Action
• ActionDef
• Event
• EventDef
• Component
• ComponentDef
• ControllerDef
• ModelDef
• AuraError
• PropertyReferenceValue

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is null.

$A.test.assertDefined()
Asserts that the value is not undefined.
Syntax

$A.test.assertDefined(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The condition to evaluate.

assertMessage String The message that is returned if the condition is not false.

$A.test.assertEquals()
Asserts that the values provided are equal. This function asserts that arg1 === arg2 is true, where arg1 is the expected value
and arg2 is the actual value.
Syntax

$A.test.assertEquals(arg1:Object, arg2:Object, assertMessage:String)

Arguments

Name Type Description

arg1 Object The first argument to evaluate against.

arg2 Object The second argument to evaluate against.

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Testing and Debugging Components Assertions

Name Type Description

assertMessage String The message that is returned if the two values are not equal.

$A.test.assertEqualsIgnoreWhitespace()
Asserts that the values provided are equal while ignoring whitespaces.
Syntax

$A.test.assertEqualsIgnoreWhitespace(arg1:Object, arg2:Object, assertMessage:String)

Arguments

Name Type Description

arg1 Object The first argument to evaluate against.

arg2 Object The second argument to evaluate against.

assertMessage String The message that is returned if the two values are not equal.

$A.test.assertFalse()
Asserts that the condition is false.
Syntax

$A.test.assertFalse(condition:Boolean, assertMessage:String)

Arguments

Name Type Description

condition Boolean The condition to evaluate.

assertMessage String The message that is returned if the condition is not false.

$A.test.assertFalsy()
Asserts that the condition is zero, an empty string, false, null, or undefined.
Syntax

$A.test.assertFalsy(condition:Boolean, assertMessage:String)

Arguments

Name Type Description

condition Boolean The condition to evaluate.

assertMessage String The message that is returned if the condition is not met.

258
Testing and Debugging Components Assertions

$A.test.assertNotEquals()
Asserts that the values provided are not equal. This function asserts that arg1 === arg2 is false, where arg1 is the expected
value and arg2 is the actual value.
Syntax

$A.test.assertNotEquals(arg1:Object, arg2:Object, assertMessage:String)

Arguments

Name Type Description

arg1 Object The first argument to evaluate against.

arg2 Object The second argument to evaluate against.

assertMessage String The message that is returned if the two values are equal.

$A.test.assertNotNull()
Asserts that the value is not null.
Syntax

$A.test.assertNotNull(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is null.

$A.test.assertNull()
Asserts that the value is null.
Syntax

$A.test.assertNull(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is not null.

$A.test.assertNotUndefinedOrNull()
Asserts that the value is not undefined or null.

259
Testing and Debugging Components Assertions

Syntax

$A.test.assertNotUndefinedOrNull(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is undefined or null.

$A.test.assertUndefined()
Asserts that the value is undefined.
Syntax

$A.test.assertUndefined(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is not undefined.

$A.test.assertUndefinedOrNull()
Asserts that the value is undefined or null.
Syntax

$A.test.assertUndefinedOrNull(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the value is not undefined or null.

$A.test.assertStartWith()
Asserts that a string starts with another.
Syntax

$A.test.assertStartWith(start:Object, full:Object, assertMessage:String)

Arguments

260
Testing and Debugging Components Assertions

Name Type Description

start Object The start string.

full Object The full string that is expected to begin with the start string.

assertMessage String The message that is returned if the full string does not begin with the start string.

$A.test.assertTrue()
Asserts that the condition is true.
Syntax

$A.test.assertTrue(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the condition is not true.

$A.test.assertTruthy()
Asserts that the condition is an object, a string, a non-zero number, a non-empty array, or true.
Syntax

$A.test.assertTrue(condition:Object, assertMessage:String)

Arguments

Name Type Description

condition Object The argument to evaluate.

assertMessage String The message that is returned if the condition is not met.

$A.test.fail()
Throws an error with the specified message, making a test fail. For example:
try {
// do something where you expect an error
$A.test.fail("should have got an error");
}
catch(e){
// assert expected error
}

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Testing and Debugging Components Debugging Components

Syntax

$A.test.fail(assertMessage:String, extraInfoMessage:String)

Arguments

Name Type Description

assertMessage String The message to return when the test fails. If not provided, the message defaults to
“Assertion failure”.

extraInfoMessage String Additional information about the test failure.

SEE ALSO:
Supporting Accessibility

Debugging Components
Use the debugger; statement to debug your JavaScript tests, with the debug console in your browser opened. Remove or comment
out the debugger; statement after you finish debugging.
You can view your debug output by appending ?aura.mode=JSTESTDEBUG to your production component, which has minimal
formatting for readability. Otherwise, append ?aura.mode=JSTEST for a minified debug output.
Another useful tool for debugging is Google Chrome's Developer Tools.
• To open Developer Tools on Windows and Linux, press Control - Shift - I in your Chrome browser.
• To quickly find which line of code a test fails on, enable the Pause on all exceptions option before running the test.
To simulate a user interaction in a test case, fire the associated Aura event. For example, use
buttonComponent.get("e.press").fire() to simulate a button click event. To fire this event in the browser console,
use $A.getRoot().find("buttonId").get("e.press").fire(). $A.getRoot() returns a reference to the top
level component. buttonId refers to the local ID of the button component.

SEE ALSO:
Debugging
Communicating with Events
Modes Reference

Utility Functions
Utility functions provide additional support for component unit tests and are prefixed with $A.test.
Aura provides the following utility functions.

$A.test.addEventHandler()
Adds an event handler. If component is specified, the handler is applied to component events. If component is not specified, the handler
will be applied to application events.

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Syntax

$A.test.addEventHandler(eventName:String, handler:Function, component:Component,

insert:Boolean)

Arguments

Name Type Description

eventName String The registered name, for component events; the descriptor name for application
events.

handler Function The function handler, which should expect the event as input.

component Component The component to add the handler on.

insert Boolean Set to true to insert the handler at the front of the list for component events only.
Otherwise, the handler is inserted at the end.

$A.test.addFunctionHandler
Adds a function handler and overrides the original function. The handler may be attached before or after the target function. If attached
after (postProcess === true), the handler will be invoked with the original function's return value followed by the original arguments.
If attached before (postProcess !== true), the handler will be invoked with just the original arguments.
Syntax

$A.test.addFunctionHandler(instance:Object, name:String, newFunction:Function,

postProcess:Boolean)

Arguments

Name Type Description

instance Object The instance of the object.

name String The name of the function whose arguments are applied to the handler.

newFunction Function The target function to attach the handler to.

postProcess Boolean Set to true if the handler is called after the target function or false if the handler is
called before the original function.

Response
The response is a function that overrides the original function. The function has a restore function that can be used to restore the
original function.

$A.test.addPrePostSendCallback
Inserts a callback either before or after sending of XHR. One of preSendCallback or postSendCallback can be null, but not
both.

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Syntax

$A.test.addPrePostSendCallback(action:Action, preSendCallback:Function,
postSendCallback:Function)

Arguments

Name Type Description

action Object The action to watch for.

preSendCallback Function The function to call before sending of XHR.

postSendCallback Function The function to call after sending of XHR.

Response
The response is a prePostConfig object to remove the callback later (needed only if the action parameter is empty).

$A.test.addPostSendCallback()
Inserts a callback after sending of XHR. For the post XHR callback, the XHR has not been sent, but actions are serialized and put in the
actual request.
Syntax

$A.test.addPostSendCallback(action:Action, postSendCallback:Function)

Arguments

Name Type Description

action Object The action to watch for.

postSendCallback Function The function to call after sending of XHR.

Response
The response is a handle to remove the callback (only needed if the action parameter is empty).

$A.test.addPreSendCallback()
Inserts a callback before sending of XHR.
Syntax

$A.test.addPreSendCallback(action:Action, preSendCallback:Function)

Arguments

Name Type Description

action Object The action to watch for.

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Name Type Description

preSendCallback Function The function to call before sending of XHR.

Response
The response is a handle to remove the callback (only needed if the action parameter is empty).

$A.test.addWaitFor
Asynchronously waits for a condition (expected === testFunction()) before continuing with the next stage of the test case.
The wait condition is checked after the current test stage is completed but before the next stage is started..
Syntax

$A.test.addWaitFor(expected:Object, testFunction:Object, callback:Function)

Arguments

Name Type Description

expected Object The value to compare against. If this is a function, it’s evaluated before comparison.

testFunction Object A function to evaluate and compare against expected.

callback Function Invoked after the comparison evaluates to true.

$A.test.addWaitForWithFailureMessage
Asynchronously waits for a condition before continuing with the next stage of the test case. The wait condition is checked after the
current test stage is completed but before the next stage is started.
Syntax

$A.test.addWaitForWithFailureMessage(expected:Object, testFunction:Object,
failureMessage:String, callback:Function)

Arguments

Name Type Description

expected Object The value to compare against. If this is a function, it’s evaluated before comparison.

testFunction Object A function to evaluate and compare against expected.

failureMessage String The message that is returned if the condition is not true.

callback Function Invoked after the comparison evaluates to true.

$A.test.addCleanup()
Add a cleanup function that is run on teardown.

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Syntax

$A.test.addCleanup(cleanupFunction:Function)

Arguments

Name Type Description

cleanupFunction Function The function to run on teardown.

$A.test.areActionsComplete()
Checks to see if an array of actions have all completed.
Syntax
$A.test.areActionsComplete()

Response
Returns true if the action state is no longer NEW or RUNNING.

$A.test.blockRequests()
Blocks requests (actions) from being sent to the server. This function is used to artificially force actions to be held on the client to be sent
to the server at a later time. It can be used to simulate delays in processing or rapid action queueing on the client.
Syntax
$A.test.blockRequests()

$A.test.blockForegroundRequests()
Blocks only foreground actions from being sent to the server.
Syntax
$A.test.blockForegroundRequests()

$A.test.blockBackgroundRequests()
Blocks only background actions from being sent to the server.
Syntax
$A.test.blockForegroundRequests()

$A.test.callServerAction
Runs a server action. The test waits for any actions to complete before running the next function. If doImmediate is set to true, the
request is sent immediately. Otherwise, the action is queued after prior requests.

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Syntax

$A.test.callServerAction(action:Action, doImmediate:Boolean)

Arguments

Name Type Description

action Action The action to run

doImmediate Boolean Set to true to send the request immediately, otherwise the action will be handled
as any other action and may be queued behind prior requests.

$A.test.clearAndAssertComponentConfigs()
Clears out component configurations returned by an action. Call this function within the action callback.
Syntax

$A.test.clearAndAssertComponentConfigs(action:Action)

Arguments

Name Type Description

action Action The action to clear.

$A.test.clickOrTouch()
Fires a click event on the element.
Syntax

$A.test.clickOrTouch(element:HTMLElement, canBubble:Boolean, cancelable:Boolean)

Arguments

Name Type Description

element HTMLElement The element to click on.

canBubble Boolean The string to look for within the other string.

cancelable Boolean Indicates whether the event is cancelable or not.

$A.test.contains()
Checks if a string contains another string.
Syntax

$A.test.contains(testString:String, targetString:String)

Arguments

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Testing and Debugging Components Utility Functions

Name Type Description

testString String The string to check

targetString String The string to look for within the other string.

Response
Returns true if testString contains targetString, or false otherwise.

$A.test.compareValues()
Compares the source and target values. For an Array or Object, this function compares first level references only. For literals, this function
compares value and type equality directly.
Syntax

$A.test.compareValues(expected:Object, actual:Object)

Arguments

Name Type Description

expected Object The source value to compare.

actual Object The target value to compare.

Response
Returns an Object that denotes the result of the comparison, with reasons.

$A.test.getGlobalValueProvider()
Returns the global value providers based on type.
Syntax

$A.test.getGlobalValueProvider(type:String)

Arguments

Name Type Description

type String The type of global value providers.

$A.test.decode()
Creates a passthrough to the JSON decode utility for tests. This function decodes a JSON string into an object.
Syntax

$A.test.decode(obj:Object, refSupport:Object)

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Testing and Debugging Components Utility Functions

Arguments

Name Type Description

obj Object The object to be decoded.

refSupport Object Optional. Resolves duplicate object references.

$A.test.enqueueAction()
Enqueues an action in an Aura call.
Syntax

$A.test.enqueueAction(action:Object, background:Boolean)

Arguments

Name Type Description

action Object The action to enqueue.

background Boolean Set to true to run the action in the background. The default value is evaluated by
action.isBackground().

$A.test.executeAfterCkEditorIsReady()
Waits for CKEditor instance in the ui:inputRichText component to be ready before continuing to enter test data.
Syntax

$A.test.executeAfterCkEditorIsReady(component:Component, callback:Function)

Arguments

Name Type Description

component Component The ui:inputRichText component, or a component that extends it.

callback Function Invoked after the CKEditor is ready for data to be set.

Response
Returns an Object that denotes the result of the comparison, with reasons.

$A.test.expectAuraWarning()
Tells the test that a warning is expected. The test fails when it does not receive the expected warning.
Syntax

$A.test.enqueueAction(msg:String)

Arguments

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Testing and Debugging Components Utility Functions

Name Type Description

w String The warning message to expect.

$A.test.findChildWithClassName()
Returns the first element on the page starting from the parent element with the specified class name.
Syntax

$A.test.findChildWithClassName(parentElement:DOMElement, className:String)

Arguments

Name Type Description

parentElement DOMElement The DOM element to start at.

className String The CSS class name.

$A.test.fireDomEvent()
Fires the DOM event for a given HTML element and event name.
Syntax

$A.test.fireDomEvent(element:Object, eventName:String, canBubble:Boolean,

cancelable:Boolean)

Arguments

Name Type Description

element Object The HTML element whose corresponding DOM event is to be fired.

eventName String Initializes the given event that bubbles up through the event chain.

canBubble Boolean Optional. Indicates whether the event can be bubbled. Defaults to true.

cancelable Boolean Optional. Indicates whether the event is cancelable or not. Defaults to true.

$A.test.getAction()
Returns an instance of an action based on the specified parameters and callback function.
Syntax

$A.test.getAction(component:Component, name:String, params:Object, callback:Function)

Arguments

Name Type Description

component Component The component on which the action is available.

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Name Type Description

name String The name of the action.

params Object The parameters to pass to the action.

callback Function The callback function to execute for the action, or if not a function, a name for the
action.

$A.test.getActiveElement()
Returns the DOMElement of the object that is currently designated as the active element.
Syntax
$A.test.getActiveElement()

$A.test.getActiveElementText()
Returns the inner text of the current active DOM element.
Syntax
$A.test.getActiveElementText()

$A.test.getAllComponentDefsFromStorage()
Returns all definitions from ComponentDefStorage.
Syntax
$A.test.getAllComponentDefsFromStorage()

$A.test.getCreationPath()
Returns the creation path, for example, /*[0] for the root component and /*[0]/$/*[0] if the body of the component appears
first in the super component.
Syntax

$A.test.getCreationPath(cmp:Component)

Arguments

Name Type Description

cmp Component The component to evaluate.

$A.test.getElementByClass()
Returns the first element on the page that has the specified class name.

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Syntax

$A.test.getElementByClass(classname:String)

Arguments

Name Type Description

className String The CSS class name.

$A.test.getErrors()
Returns errors as JSON encoded strings. If no errors are found, return an empty string.

$A.test.getExternalAction
Returns an instance of a server action that’s unavailable to the component.
Syntax

$A.test.getExternalAction(component:Component, descriptor:String, params:Object,

returnType:Object, callback:Function)

Arguments

Name Type Description

component Component The component to run the action with, even if the action is not available to it.

descriptor String The descriptor for the action, for example,

java://my.own.Controller/ACTION$doIt

params Object The parameters to pass to the action.

returnType Object The return type descriptor for the action, for example,
java://java.lang.String

callback Function An optional callback to execute with the component

$A.test.getOuterHtml(node)
Returns the outer HTML of an element.

$A.test.getPrototype()
Returns the prototype of the instance or object.
Syntax

$A.test.getPrototype(instance:Object)

Arguments

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Testing and Debugging Components Utility Functions

Name Type Description

instance Object The instance of the object

$A.test.getAction(component, name, params, callback)

Returns an instance of an action.

$A.test.getElementAttributeValue()
Returns attribute value of an element.
Syntax

$A.test.getElementAttributeValue(element:HTMLElement, attributeName:String)

Arguments

Name Type Description

element HTMLElement The element from which to retrieve data.

attributeName String The name of attribute to look up on element.

$A.test.getErrors()
Returns the list of errors for the test, not including any errors handled explicitly by the framework.
Syntax
$A.test.getErrors()

Response
Returns an empty string if there are no errors, or a JSON encoded list of errors.

$A.test.getOuterHtml()
Returns a DOM node’s outer HTML markup.
Syntax

$A.test.getOuterHtml(node:Node)

Arguments

Name Type Description

node Node The node from which to get the outer HTML

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$A.test.getNonCommentNodes()
Filters out comment nodes from a list of nodes.
Syntax

$A.test.getNonCommentNodes(nodes:Array|Object)

Arguments

Name Type Description

nodes Array|Object The list of nodes to filter

$A.test.getSentRequestCount()
Returns total count of foreground and background requests sent to the server. This function can be used to get a before and after count
on server requests to verify that only the necessary requests are being sent.
Syntax
$A.test.getSentRequestCount()

$A.test.getStyle()
Returns the CSS property value for a style for the specified DOMElement.
Syntax

$A.test.getStyle(elem:DOMElement, style:String)

Arguments

Name Type Description

elem DOMElement The node from which to get the text content.

style String The property name to retrieve.

$A.test.getTestName()
Returns the test name.
Syntax
$A.test.getTestName()

$A.test.getText()
Returns text content of a DOM node. Tries textContent, followed by innerText and nodeValue to consider browser
differences.

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Testing and Debugging Components Utility Functions

Syntax

$A.test.getText(node:Node)

Arguments

Name Type Description

node Node The node from which to get the text content.

$A.test.getTextByComponent()
Returns text content rendered by a component.
Syntax

$A.test.getTextByComponent(component:Component)

Arguments

Name Type Description

component Component The component from which to get the text content.

$A.test.isActionPending()
Checks if there are pending server actions.
Syntax
$A.test.isActionPending()

Response
Returns true if there are pending server actions, or false otherwise.

$A.test.isActionQueued()
Checks if there are queued server actions.
Syntax
$A.test.isActionQueued()

Response
Returns true if there are queued server actions, or false otherwise.

$A.test.isComplete()
Checks if the test has finished running.
Syntax
$A.test.isComplete()

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Testing and Debugging Components Utility Functions

Response
Returns true if the test has completed, or false otherwise.

$A.test.isInstanceOf()
Checks if an element is an instance of another element.
Syntax

$A.test.isInstanceOf(element:HTMLElement, elementType:HTMLElement, tag:String)

Arguments

Name Type Description

element HTMLElement The element to check.

elementType HTMLElement Checks element against elementType.

tag String Checks element.tagName against tag.

Response
Returns true if the element is of type elementType. If elementType is undefined, check element is of type ELEMENT_NODE
and its tagName is equal to tag.

$A.test.isInstanceOfAnchorElement()
Checks if an element is an anchor element.
Syntax

$A.test.isInstanceOfAnchorElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is an anchor element, or false otherwise.

$A.test.isInstanceOfButtonElement()
Checks if an element is a button element.
Syntax

$A.test.isInstanceOfButtonElement(element:HTMLElement)

Arguments

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Testing and Debugging Components Utility Functions

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is a button element, or false otherwise.

$A.test.isInstanceOfDivElement()
Checks if an element is a div element.
Syntax

$A.test.isInstanceOfDivElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is a div element, or false otherwise.

$A.test.isInstanceOfImageElement()
Checks if an element is an image element.
Syntax

$A.test.isInstanceOfImageElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is an image element, or false otherwise.

$A.test.isInstanceOfInputElement()
Checks if an element is an input element.
Syntax

$A.test.isInstanceOfInputElement(element:HTMLElement)

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Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is an input element, or false otherwise.

$A.test.isInstanceOfLiElement()
Checks if an element is a list element.
Syntax

$A.test.isInstanceOfLiElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is a list element, or false otherwise.

$A.test.isInstanceOfParagraphElement()
Checks if an element is a paragraph element.
Syntax

$A.test.isInstanceOfParagraphElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is a paragraph element, or false otherwise.

$A.test.isInstanceOfSpanElement()
Checks if an element is a span element.

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Syntax

$A.test.isInstanceOfSpanElement(element:HTMLElement)

Arguments

Name Type Description

element HTMLElement The element to check

Response
Returns true if the element is a span element, or false otherwise.

$A.test.isInstanceOfText()
Checks if a node is a text node.
Syntax

$A.test.isInstanceOfText(node:Node)

Arguments

Name Type Description

node Node The node to check

Response
Returns true if the node is a text node, or false otherwise.

$A.test.isNodeDeleted()
Checks if a node has been deleted by the framework.
Syntax

$A.test.isNodeDeleted(node:Node)

Arguments

Name Type Description

node Node The node to check

Response
Returns true if the node has been deleted, or false otherwise.

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$A.test.orderedEncode()
Serializes object in alphabetical ascending order. Sorts object keys during serialization.
Syntax

$A.test.orderedEncode(obj:Object)

Arguments

Name Type Description

obj Object The object to serialize.

Response
Returns a string of serialized order object.

$A.test.overrideFunction()
Replaces a function on an object with a restorable override.
Syntax

$A.test.overrideFunction(instance:Object, name:String, newFunction:Function)

Arguments

Name Type Description

instance Object The instance of the object.

name String The name of the function to be replaced.

newFunction String The new function that replaces the original function.

Response
The response is a function that overrides the original function. The function has a restore function that can be used to restore the
original function.

$A.test.releaseRequests()
Releases requests (actions) to be sent to the server. Call this function after $A.test.blockRequests() only. You can’t release
requests that are not blocked.
Syntax
$A.test.releaseRequests()

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$A.test.releaseForegroundRequests()
Releases only foreground requests from being sent to the server. Call this function after $A.test.blockRequests() only. You
can’t release requests that are not blocked.
Syntax
$A.test.releaseForegroundRequests()

$A.test.releaseBackgroundRequests()
Releases only background requests from being sent to the server. Call this function after $A.test.blockRequests() only. You
can’t release requests that are not blocked.
Syntax
$A.test.releaseForegroundRequests()

$A.test.run()
Runs the test.
Syntax

$A.test.run(name:String, code:String, timeoutOverride:Integer)

Arguments

Name Type Description

name String A list of actions to run.

code String The scope for the callback

timeoutOverride Integer Optional. Increases the test timeout in seconds. The default is 10 seconds.

$A.test.runActionAsTransaction()
Runs a set of actions as a transaction. This function wraps around $A.test.runActions() to allow a test to safely run a set of
actions as a single transaction with a callback.
Syntax

$A.test.runActionAsTransaction(actions:Array, scope:Object, callback:Function)

Arguments

Name Type Description

actions Array A list of actions to run.

scope Object The scope for the callback

callback Function The callback function to execute for the action

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$A.test.runAfterIf
Runs a callback after conditionFunction evaluates to truthy, checking the condition at the specified interval. Truthy values can
refer to a non-empty string, a non-zero number, a non-empty array, an object, or an expression evaluating to true.
Syntax

$A.test.runAfterIf(conditionFunction:Function, callback:Function, intervalInMs:Number)

Arguments

Name Type Description

conditionFunction Function The function to evaluate.

callback Function The callback function to run if the condition evaluates to truthy

intervalInMs Number The number of milliseconds between each evaluation of the condition. The default
is 500 milliseconds.

$A.test.select()
Returns a list of nodes and passes each argument as a separate parameter.
Syntax
$A.test.select()

$A.test.setTestTimeout()
Sets the timeout in a period of milliseconds from now, clearing the existing timeout.
Syntax

$A.test.setTestTimeout(timeoutMs:Number)

Arguments

Name Type Description

timeoutMs Number The number of milliseconds from now in which the test should timeout.

$A.test.storageAdapterSetItems()
Stores items to storage through the storage’s adapter, bypassing the key prefix and size validation logic AuraStorage performs.
Syntax

$A.test.storageAdapterSetItems(adapter:StorageAdapter, tuples:Array)

Arguments

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Testing and Debugging Components Sample Test Cases

Name Type Description

adapter StorageAdapter The storage adapter on which to store the items

tuples Array An array of key-value-size pairs

SEE ALSO:
Assertions

Sample Test Cases

Testing Label Values

This component contains two link buttons that save or cancel an action.
<!-- Component markup -->
<ui:outputURL label="Cancel" value="#" class="secondary-button" linkClick="{!c.onCancel}"/>
<ui:outputURL label="Save" value="#" class="primary-button" linkClick="{!c.onSave}"/>

The following test case uses assert statements to check that labels on the link buttons are set correctly. If you’re using the global value
provider $Label to set the label value in the component, use $A.get("$Label.myLabel") to retrieve the label.
({
browsers: ["-IE7", "-IE8"], //optional browser exclusion
testButtons : {
test : [
function testCancelButton(cmp) {
$A.test.assertEquals(1, $A.test.select('.secondary-button').length,
'Cancel button is not being displayed.');

$A.test.assertEquals("Cancel",
$A.test.getText($A.test.select('.secondary-button')[0]),
'Cancel button label is not set correctly.');
},

function testSaveButton(cmp) {
$A.test.assertEquals(1, $A.test.select('.primary-button').length,
'Save button is not being displayed.');

$A.test.assertEquals("Save",
$A.test.getText($A.test.select('.primary-button')[0]),
'Save button label is not set correctly.');
}
]
}
})

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Testing Attribute Values

This component contains an input text area component with an attribute that sets the maximum number of characters.
<aura:attribute name="maxLength" type="Integer" default="5000"
description="Max number of chars that can be inserted"/>
<ui:inputTextArea aura:id="textarea" label="My input"/>

The following test case checks that the attribute maxLength is correctly set.
{(
testMaxLength:{
attributes : { maxLength: 10 },
test : function(cmp){
cmp.set("v.value", "1234567890");
cmp.getDef().getHelper().onValueChange(cmp);
$A.test.assertEquals(0, this.getErrorCount(cmp), "No errors found");

cmp.set("v.value", "12345678901");
cmp.getDef().getHelper().onValueChange(cmp);
$A.test.assertEquals(1, this.getErrorCount(cmp), "Too many characters");
}
}
})

Testing HTML Elements

This component contains a div tag with a class attribute that is set on rendering.
<!-- Component Markup -->
<aura:attribute name="class" type="String" default="" description="Additional css classes"/>
<div aura:id="myCmp" class="{! 'myClass ' + v.class}">
<!-- Other component markup -->
</div>

The following test case checks that the specified class is set on initial render and rerender.
({
verifyMyCmp: function(cmp) {
var ele = cmp.find("myCmp").getElement();
$A.test.assertTrue($A.util.hasClass(ele, "myClass"), "Element is not rendered with
myClass");

// additional class
if(cmp.get("v.class")) {
$A.test.assertTrue($A.util.hasClass(ele, cmp.get("v.class")), "Additional class
not added as expected");
}
else {
$A.test.assertTrue($A.util.hasClass(ele, "testClass"), "Additional class added
unexpectedly");
}
},
testMyCmp: {
attributes: {

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isVisible: true, //myCmp is rendered

'class': "testClass",
},
test: function(cmp) {
this.verifyMyCmp(cmp);
}
}
})

SEE ALSO:
JavaScript Test Suite Setup

Mocking Java Classes

Use mocking to isolate your JavaScript test from other resources, such as a Java model, provider, or server-side controller. This enables
you to narrow the focus of the test and eliminate other modes of failure, such as network errors. You should test the external resources
in separate tests.
Aura enables you to mock a Java model, provider, or server-side controller by using a mocks element in your test function. mocks
is an array of objects representing the resource that you're mocking.
Let's look at the high-level structure of a test using a mocked object. mocks contains type, stubs, and descriptor elements.
testSampleSyntax : {
mocks : [{
type : "MODEL|PROVIDER|ACTION",
// descriptor is optional
descriptor : ...,
stubs : [{
// method is optional for a model or provider
method : { ... },
answers : [{
// specify value or error but not both
value : ...
error : ...
}]
}]
}],
test : function(cmp) {
// test code goes here
}
},

type
The type of mock object. Valid values are: MODEL, PROVIDER, and ACTION.

stubs
An array of objects representing the Java methods of the class being mocked. A stub object has method and answers properties.

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Testing and Debugging Components Mocking Java Classes

method
The method property is optional, except for the ACTION type. It defaults to provide for a provider, and newInstance for a
model.
A method has the following elements:
• name is the method name.
• params is an array of Strings representing the input parameter types, if there are parameters.
• type is the return type. The default value is Object.
For example, this method element mocks String doSomeWork(Boolean immediate, MyCustomType toProcess).
method : {
name : "doSomeWork",
type : "java.lang.String",
params : ["java.lang.Boolean","my.package.MyCustomType"]
}

answers
The answers property is an array of answer objects returned by the stub when it is invoked.
An answer object has either a value or an error property. This indicates whether the mock returns the given value or throws a
Java exception.
The format of the value object depends on the class being mocked. Provider values correspond to the ComponentConfig object
returned by provide(), and can specify either descriptor or attributes or both.

Note: The framework doesn't support custom values, such as types that require a custom converter.

Multiple answers enable you to test sequencing or multiple invocations of an action. For example, if a test simulates clicking a button
twice, this would call a server action twice, and you may want the actions to return different responses.
Alternatively, your component might load two or more input fields and you want the model to return different values for each field. If
the mock is invoked more times than you have answers for, the last answer is repeated. For example, if the mock for an input field value
returns the answers "anybody" and "there", but the component has four input fields, the mock returns "anybody", "there", "there", "there".
The error property is a String containing the fully qualified class name of the exception thrown. You can only use exceptions
with no-argument constructors, or a constructor accepting a String.

descriptor
The descriptor element is optional and defaults to the descriptor for the resource being mocked. For example, this is the descriptor
for a model class.
descriptor : "java://org.auraframework.docsample.SampleJavaModel",

To mock the type of a super or child component, such as a child ui:input component, you need to specify a descriptor.

Note: The descriptor for the ACTION type is the controller descriptor rather than the action descriptor. For example:
descriptor : "java://org.auraframework.docsample.SampleJavaController",

286
Testing and Debugging Components Mocking Java Models

IN THIS SECTION:
Mocking Java Models
Mocking Java Providers
Mocking Java Actions

Mocking Java Models

This test mocks a Java model. The test function is a placeholder. You would add actual test code here.
testModelProperties : {
mocks : [{
type : "MODEL",
stubs : [{
answers : [{
value : {
secret : { value : "<not available>" } ,
integer : { value : 1 },
stringList : { value : [ "early", "on", "time", "late"] }
}
}]
}]
}],
test : function(cmp) {
// test code goes here
}
},

This test has a mock object that throws an exception.

testModelThrowsException : {
mocks : [{
type : "MODEL",
stubs : [{
answers : [{
error : "org.auraframework.throwable.AuraRuntimeException"
}]
}]
}],
test : function(cmp) {
// test code goes here
}
},

SEE ALSO:
Java Models
Mocking Java Providers
Mocking Java Actions
Mocking Java Classes

287
Testing and Debugging Components Mocking Java Providers

Mocking Java Providers

This test mocks a Java provider. The test function is a placeholder. You would add actual test code here.
testProviderDescriptorAndAttributes : {
mocks : [{
type : "PROVIDER",
stubs : [{
answers : [{
value : {
descriptor : "aura:text",
attributes : { value : "fresh"}
}
}]
}]
}],
test : function(cmp) {
// test code goes here
}
},

The value element for a provider corresponds to the ComponentConfig object returned by provide(), and can specify either
descriptor or attributes or both.

SEE ALSO:
Server-Side Runtime Binding of Components
Mocking Java Models
Mocking Java Actions
Mocking Java Classes

Mocking Java Actions

This test mocks an action in a Java server-side controller. The test function is a placeholder. You would add actual test code here.
testActionString : {
mocks : [{
type : "ACTION",
stubs : [{
method : { name : "getString" },
answers : [{
value : "what I expected"
}]
}]
}],
test : function(cmp) {
// test code goes here
}
},

This test has a mock object that throws an exception.

testModelThrowsException : {
mocks : [{

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Testing and Debugging Components Mocking Java Actions

type : "ACTION",
stubs : [{
method : { name : "getString" },
answers : [{
error : "java.lang.IllegalStateException"
}]
}]
}],
test : function(cmp) {
// test code goes here
}
}

SEE ALSO:
Creating Server-Side Logic with Controllers
Mocking Java Models
Mocking Java Providers

289
CHAPTER 7 Customizing Behavior with Modes
In this chapter ... Modes are used to customize Aura framework behavior. For example, the framework is optimized for
performance in PROD (production) mode, and ease of debugging in DEV (development) mode.
• Modes Reference
• Controlling Available
Modes
• Setting the Default
Mode
• Setting the Mode for
a Request

290
Customizing Behavior with Modes Modes Reference

Modes Reference
Aura supports different modes, which are useful depending on whether you are developing, testing, or running code in production. The
list of modes in Aura is defined in the AuraContext Java interface.
Every request in Aura is associated with a context. After initial loading of an app, each subsequent request is an XHR POST that contains
your Aura context configuration, which includes the mode to run in, and the name of the app.
We split the list of modes into two sections here to differentiate between runtime and test modes. This split is purely to cluster similar
modes together in the documentation. All the runtime and core modes are defined in the Mode enum in AuraContext.
All modes are available by default in your app. Many of the modes use the Google Closure Compiler, which is a tool for optimizing
JavaScript code.

Runtime Modes
Use these modes for running in development or production.

Mode PROD DEV PRODDEBUG

Usage Use for apps in production. The Use for apps in development. Use temporarily to debug apps
framework is optimized for The framework is configured for in production.
performance rather than ease of ease of debugging in this mode.
debugging in this mode.

Debugging Not recommended for Facilitates debugging. Pretty Facilitates debugging. JavaScript
debugging. prints JSON responses from the is non-minified and readable.
Since PROD mode is intended server. Exposes private members
for apps in production, test in some framework JavaScript
modes, such as SELENIUM, are objects.
preferable for running tests,
especially concurrent tests.

Access Disables access to a .cmp Enables a .cmp resource to be Similar to PROD mode
resource in a URL. You can only addressed in a URL.
access a .app resource.

Google Closure Compiler Uses the Google Closure Uses the Google Closure Does not use Google Closure
Compiler to optimize the Compiler to lightly obfuscate the Compiler
JavaScript code. The method names of non-exported
names and code are heavily JavaScript methods. This is
obfuscated. meant to avoid unintentional
usage of non-exported methods.

Caching Caches code. When a file change Caches code. When a file change Similar to PROD mode
is detected, this mode performs is detected, this mode clears the
a full closure compile on all cache and recompiles
units. definitions.

291
Customizing Behavior with Modes Modes Reference

Test Modes
Use these modes for running different flavors of tests. The various test modes mainly expose extra JavaScript calls that are not available
in runtime modes.
In all test modes, caching of registries between tests is disabled. If you modify a cached definition in a test, the modified cached definition
is not visible to subsequent tests.

Mode Usage
JSTEST Use for running component tests. If your component or app has a
<componentName>Test.js file in its bundle, a browser page is displayed to run the
tests. A tab is displayed for each test case in your test suite. Each tab contains an iframe that
loads the component in AUTOJSTEST mode and runs the single test case.
The test results are displayed below the iframe. For a successful test run, the tab turns green;
for a failure, it turns red.

JSTESTDEBUG Use for debugging component tests. Similar to JSTEST mode but doesn’t use the Google
Closure Compiler.

AUTOJSTEST Used by JSTEST mode when running inside the iframe for a test case. It enables extra
JavaScript needed to execute the test case.
Use this mode by requesting the component or app containing the test in JSTEST mode.

AUTOJSTESTDEBUG Used by JSTESTDEBUG mode when running inside the iframe for a test case. It enables
extra JavaScript needed to execute the test case.
Use this mode by requesting the component or app containing the test in JSTESTDEBUG
mode.

PTEST Use for running performance tests using the Jiffy Graph UI. Loads Jiffy performance test
tools and enables the Jiffy Graph UI. Jiffy is an end-to-end real-world web page
instrumentation and measurement suite.
This mode doesn’t use the Google Closure Compiler.

CADENCE Use for running performance tests if you want to use Jiffy metrics and track the numbers
server-side. Loads and runs Jiffy performance test tools and logs the results on the server.
Cadence tests use Jiffy, but don’t load the Jiffy Graph UI.

SELENIUM Use for tests with Selenium, a software testing framework for web apps. This mode uses the
Google Closure Compiler.

SELENIUMDEBUG Similar to SELENIUM mode but doesn’t use the Google Closure Compiler.

UTEST Used for running unit tests against the framework. It allows developers of the framework
to enable some debug code only during testing.

292
Customizing Behavior with Modes Controlling Available Modes

Mode Usage
FTEST Similar to UTEST mode, but used for functional tests instead of unit tests. This mode may
expose different debug code than UTEST mode.

SEE ALSO:
Component Bundles
Setting the Default Mode
Testing and Debugging Components

Controlling Available Modes

You can customize the set of available modes in your application by writing a Java class that implements the getAvailableModes()
method in the ConfigAdapter interface. The default implementation in ConfigAdapterImpl makes all modes available.
So, if you want to use your own configuration to limit the modes in certain environments, such as a production environment, you could
limit the modes to only allow PROD mode. This would ensure that PROD mode is used for all requests. The default mode is not used
if it’s not also included in the list of available modes.

SEE ALSO:
Modes Reference
Setting the Default Mode
Setting the Mode for a Request

Setting the Default Mode

The default mode is DEV. This is defined in the ConfigAdapterImpl Java class.
You can change the default mode to PROD by setting the aura.production Java system property to true. Do this by adding
-Daura.production=true to the arguments when you are starting your server.
To set an alternate default mode, write a Java class that implements the getDefaultMode() method in the ConfigAdapter
Java interface.
The default mode is not used if it’s not also included in the list of available modes.

SEE ALSO:
Controlling Available Modes
Setting the Mode for a Request
Modes Reference

293
Customizing Behavior with Modes Setting the Mode for a Request

Setting the Mode for a Request

Each application has a default mode, but you can change the mode for each HTTP request by setting the aura.mode parameter in
the query string. If the requested mode is in the list of available modes, the response for that mode is returned. Otherwise, the default
mode is used.
For example, let’s assume that DEV and PROD are in the set of the available modes. If the default mode is DEV and you want to see
the response in PROD mode, use aura.mode=PROD in the query string of the request URL. For example:
http://<your server>/demo/test.app?aura.mode=PROD

SEE ALSO:
Modes Reference
Setting the Default Mode
Controlling Available Modes
URL-Centric Navigation

294
CHAPTER 8 Debugging
In this chapter ... There are a few basic tools and techniques that can help you to debug applications.
Use Chrome DevTools to debug your client-side code.
• Log Messages
• Warning Messages • To open DevTools on Windows and Linux, press Control-Shift-I in your Google Chrome browser. On
Mac, press Option-Command-I.
• To quickly find which line of code is failing, enable the Pause on all exceptions option before
running your code.
To learn more about debugging JavaScript on Google Chrome, refer to the Google Chrome's DevTools
website.

295
Debugging Log Messages

Log Messages
To help debug your client-side code, you can write output to the JavaScript console of a web browser using console.log() if your
browser supports it..
For instructions on using the JavaScript console, refer to the instructions for your web browser.
Use the $A.log(string[, error]) method to output a log message to the JavaScript console.
The first parameter is the string to log.
The optional second parameter is an error object that can include more detail.

Note: $A.log() doesn't output by default in PROD or PRODDEBUG modes. To log messages in PROD or PRODDEBUG
modes, see Logging in Production Modes on page 296. Alternatively, use console.log() if your browser supports it.
For example, $A.log("This is a log message") outputs to the JavaScript console:
This is a log message

Adding $A.log("The name of the action is: " + this.getDef().getName()) in an action called openNote
in a client-side controller outputs to the JavaScript console:
The name of the action is: openNote

The output is also sent to the Aura Debug Tool.

Logging in Production Modes

To log messages in PROD or PRODDEBUG modes, write a custom logging function. You must use
$A.logger.subscribe(String level, function callback) to subscribe to log messages at a certain severity
level.
The first parameter is the severity level you're subscribing to. The valid values are:
• ASSERT
• ERROR
• INFO
• WARNING
The second parameter is the callback function that will be called when a message at the subscribed severity level is logged.
Note that $A.log() logs a message at the INFO severity level. Adding $A.logger.subscribe("INFO", logCustom)
causes $A.log() to log using the custom logCustom() function you define.
Let's look at some sample JavaScript code in a client-side controller.
({
sampleControllerAction: function(cmp) {
// subscribe to severity levels
$A.logger.subscribe("INFO", logCustom);
// Following subscriptions not exercised here but shown for completeness
//$A.logger.subscribe("WARNING", logCustom);
//$A.logger.subscribe("ASSERT", logCustom);
//$A.logger.subscribe("ERROR", logCustom);

$A.log("log one arg");

296
Debugging Warning Messages

$A.log("log two args", {message: "drat and double drat"});

function logCustom(level, message, error) {

console.log(getTimestamp(), "logCustom: ", arguments);
}

function getTimestamp() {
return new Date().toJSON();
}
}

})

$A.logger.subscribe("INFO", logCustom) subscribes so that messages logged at the INFO severity level will call the
logCustom() function. In this case, logCustom() simply logs the message to the console with a timestamp.
The $A.log() calls log messages at the INFO severity level, which matches the subscription and invokes the logCustom()
callback.

Warning Messages
To help debug your client-side code, you can use the warning() method to write output to the JavaScript console of your web
browser.
Use the $A.warning(string) method to write a warning message to the JavaScript console. The parameter is the message to
display.
For example, $A.warning("This is a warning message."); outputs to the JavaScript console.
This is a warning message.

The output is also sent to the Aura Debug Tool.

Note: $A.warning() doesn't output by default in PROD or PRODDEBUG modes. To log warning messages in PROD or
PRODDEBUG modes, use $A.logger.subscribe("WARNING", logCustom), where logCustom() is a custom
function that you define. For more information, see Logging in Production Modes on page 296.
For instructions on using the JavaScript console, refer to the instructions for your web browser.

297
CHAPTER 9 Fixing Performance Warnings
In this chapter ... A few common performance anti-patterns in code prompt the framework to log warning messages to
the browser console. Fix the warning messages to speed up your components!
• <aura:if>—Clean
Unrendered Body
The warnings display in the browser console only if you enabled debug mode.

• <aura:iteration>—Multiple
Items Set SEE ALSO:
Enable Debug Mode for Lightning Components

298
Fixing Performance Warnings <aura:if>—Clean Unrendered Body

<aura:if>—Clean Unrendered Body

This warning occurs when you change the isTrue attribute of an <aura:if> tag from true to false in the same rendering
cycle. The unrendered body of the <aura:if> must be destroyed, which is avoidable work for the framework that slows down
rendering time.

Example
This component shows the anti-pattern.
<!--c:ifCleanUnrendered-->
<aura:component>
<aura:attribute name="isVisible" type="boolean" default="true"/>
<aura:handler name="init" value="{!this}" action="{!c.init}"/>

<aura:if isTrue="{!v.isVisible}">
<p>I am visible</p>
</aura:if>
</aura:component>

Here’s the component’s client-side controller.

/* c:ifCleanUnrenderedController.js */
({
init: function(cmp) {
/* Some logic */
cmp.set("v.isVisible", false); // Performance warning trigger
}
})

When the component is created, the isTrue attribute of the <aura:if> tag is evaluated. The value of the isVisible attribute
is true by default so the framework creates the body of the <aura:if> tag. After the component is created but before rendering,
the init event is triggered.
The init() function in the client-side controller toggles the isVisible value from true to false. The isTrue attribute
of the <aura:if> tag is now false so the framework must destroy the body of the <aura:if> tag. This warning displays in
the browser console only if you enabled debug mode.
WARNING: [Performance degradation] markup://aura:if ["5:0"] in c:ifCleanUnrendered ["3:0"]
needed to clear unrendered body.

Click the expand button beside the warning to see a stack trace for the warning.

Click the link for the ifCleanUnrendered entry in the stack trace to see the offending line of code in the Sources pane of the
browser console.

299
Fixing Performance Warnings <aura:iteration>—Multiple Items Set

How to Fix the Warning

Reverse the logic for the isTrue expression. Instead of setting the isTrue attribute to true by default, set it to false. Set the
isTrue expression to true in the init() method, if needed.
Here’s the fixed component:
<!--c:ifCleanUnrenderedFixed-->
<aura:component>
<!-- FIX: Change default to false.
Update isTrue expression in controller instead. -->
<aura:attribute name="isVisible" type="boolean" default="false"/>
<aura:handler name="init" value="{!this}" action="{!c.init}"/>

<aura:if isTrue="{!v.isVisible}">
<p>I am visible</p>
</aura:if>
</aura:component>

Here’s the fixed controller:

/* c:ifCleanUnrenderedFixedController.js */
({
init: function(cmp) {
// Some logic
// FIX: set isVisible to true if logic criteria met
cmp.set("v.isVisible", true);
}
})

SEE ALSO:
Enable Debug Mode for Lightning Components

<aura:iteration>—Multiple Items Set

This warning occurs when you set the items attribute of an <aura:iteration> tag multiple times in the same rendering cycle.
There’s no easy and performant way to check if two collections are the same in JavaScript. Even if the old value of items is the same
as the new value, the framework deletes and replaces the previously created body of the <aura:iteration> tag.

Example
This component shows the anti-pattern.
<!--c:iterationMultipleItemsSet-->
<aura:component>
<aura:attribute name="groceries" type="List"
default="[ 'Eggs', 'Bacon', 'Bread' ]"/>

<aura:handler name="init" value="{!this}" action="{!c.init}"/>

<aura:iteration items="{!v.groceries}" var="item">

<p>{!item}</p>

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Fixing Performance Warnings <aura:iteration>—Multiple Items Set

</aura:iteration>
</aura:component>

Here’s the component’s client-side controller.

/* c:iterationMultipleItemsSetController.js */
({
init: function(cmp) {
var list = cmp.get('v.groceries');
// Some logic
cmp.set('v.groceries', list); // Performance warning trigger
}
})

When the component is created, the items attribute of the <aura:iteration> tag is set to the default value of the groceries
attribute. After the component is created but before rendering, the init event is triggered.
The init() function in the client-side controller sets the groceries attribute, which resets the items attribute of the
<aura:iteration> tag. This warning displays in the browser console only if you enabled debug mode.

WARNING: [Performance degradation] markup://aura:iteration [id:5:0] in

c:iterationMultipleItemsSet ["3:0"]
had multiple items set in the same Aura cycle.

Click the expand button beside the warning to see a stack trace for the warning.

Click the link for the iterationMultipleItemsSet entry in the stack trace to see the offending line of code in the Sources
pane of the browser console.

How to Fix the Warning

Make sure that you don’t modify the items attribute of an <aura:iteration> tag multiple times. The easiest solution is to
remove the default value for the groceries attribute in the markup. Set the value for the groceries attribute in the controller
instead.
The alternate solution is to create a second attribute whose only purpose is to store the default value. When you’ve completed your
logic in the controller, set the groceries attribute.
Here’s the fixed component:
<!--c:iterationMultipleItemsSetFixed-->
<aura:component>
<!-- FIX: Remove the default from the attribute -->
<aura:attribute name="groceries" type="List" />
<!-- FIX (ALTERNATE): Create a separate attribute containing the default -->
<aura:attribute name="groceriesDefault" type="List"
default="[ 'Eggs', 'Bacon', 'Bread' ]"/>

301
Fixing Performance Warnings <aura:iteration>—Multiple Items Set

<aura:handler name="init" value="{!this}" action="{!c.init}"/>

<aura:iteration items="{!v.groceries}" var="item">

<p>{!item}</p>
</aura:iteration>
</aura:component>

Here’s the fixed controller:

/* c:iterationMultipleItemsSetFixedController.js */
({
init: function(cmp) {
// FIX (ALTERNATE) if need to set default in markup
// use a different attribute
// var list = cmp.get('v.groceriesDefault');
// FIX: Set the value in code
var list = ['Eggs', 'Bacon', 'Bread'];
// Some logic
cmp.set('v.groceries', list);
}
})

SEE ALSO:
Enable Debug Mode for Lightning Components

302
CHAPTER 10 Measuring Performance with MetricsService
In this chapter ... MetricsService enables you to instrument and measure the performance of your code and the
framework during development, testing, or production usage. With MetricsService, you can
• Adding Performance abstract your performance marks and measures using plugins. This leads to a clean separation between
Transactions functional code and instrumentation code that measures the performance of the functional code.
• Adding Performance
The framework is well instrumented already. You can take advantage of the underlying framework
Marks
measurements and get insight into the performance of your code by adding a mark or transaction.
• Logging Data with
Beacons Here are some core concepts for the MetricsService.
• Abstracting Mark
Measurement with A mark measures a specific event. Use a mark to measure an interval of a larger transaction.
Plugins Transaction
• End-to-End A transaction enables you to track all optional marks that occur in between the transaction start and
MetricsService end time. A mark measures a specific event. A transaction that doesn't contain any marks still tracks
Example useful information about the time taken to complete an operation.
Beacon
A beacon is a component that receives the metrics and sends them somewhere for storage. A beacon
abstracts the transport layer for sending collected metrics and transactions.
Plugin
A plugin hooks into the code being measured and enables you to instrument your functional code
without adding performance marks directly in your functional code. Add the performance marks in
the plugin so that your functional code doesn't get littered with marks. This leads to a clean separation
between functional code and instrumentation code that measures the performance of the functional
code.
A plugin uses AOP (aspect-oriented programming) and the MetricsService API calls to hook
into the code being measured.

303
Measuring Performance with MetricsService Adding Performance Transactions

Adding Performance Transactions

A transaction enables you to track all optional marks that occur in between the transaction start and end time. A mark measures a specific
event. A transaction that doesn't contain any marks still tracks useful information about the time taken to complete an operation.
A transaction gives you information about marks that you don’t control or own. For example, your transaction could include framework-level
marks to track a server request or action caching. This framework-level benchmarking comes for free and can give you valuable insight
into the performance of your code.
You can add a transaction directly in your code. Consider adding a transaction when you want to measure an action in production that
involves a server trip. This gives you performance data that factors in network latency. You don’t need transactions for purely client-side
operations as those operations are adequately tested in framework code.

Starting a Transaction
To start a transaction, use $A.metricsService.transactionStart(). The syntax is:
transactionStart(String ns, String name, Object config)

The parameters are:

String ns
Optional. Transaction namespace. You can use any value. This parameter doesn't have anything to do with a component's namespace
though you can use the component's namespace as a high-level identifier.
String name
Transaction name. You can use any value, such as a component or action's name.
Object config
Optional custom data to log. Keys in the object are:
Object context: Custom data for the transaction
function postProcess: The function to execute before sending the transaction to the beacon
Boolean skipPluginPostProcessing: If true, skip all post processing. This is always set to true in PROD mode.

Ending a Transaction
To end a transaction, use $A.metricsService.transactionEnd(). The syntax is:
transactionEnd(String ns, String name, Object config | function)

The parameters are:

String ns
Optional. Transaction namespace. You can use any value. This parameter doesn't have anything to do with a component's namespace
though you can use the component's namespace as a high-level identifier.
String name
Transaction name. You can use any value, such as a component or action's name.
Object config | function
Optional. This parameter can be an Object or a function. The Object contains any custom data that you want to log. If a
function is set instead, the function is executed before sending the transaction to the beacon. Keys in the object are:
Object context: Custom data for the transaction

304
Measuring Performance with MetricsService Adding Performance Transactions

function postProcess: The function to execute before sending the transaction to the beacon
Boolean skipPluginPostProcessing: If true, skip all post processing. This is always set to true in PROD mode.

Tracking a Specific User Action

To track a specific user action, use $A.metricsService.transaction(). Tracking a user taking a specific UI action, such as
clicking a specific button, can be useful if you want to analyze these UI actions later. The syntax is:
transaction(String ns, String name, Object config | function)

The parameters are:

String ns
Optional. Transaction namespace. You can use any value. This parameter doesn't have anything to do with a component's namespace
though you can use the component's namespace as a high-level identifier.
String name
Transaction name. You can use any value, such as a component or action's name.
Object config | function
Optional. This parameter can be an Object or a function. The Object contains any custom data that you want to log. If a
function is set instead, the function is executed before sending the transaction to the beacon. Keys in the object are:
Object context: Custom data for the transaction
function postProcess: The function to execute before sending the transaction to the beacon
Boolean skipPluginPostProcessing: If true, skip all post processing. This is always set to true in PROD mode.

Hook for Callback After Every Transaction Ends

To set a callback to be executed after every transaction ends, use $A.metricsService.onTransactionEnd(). The syntax
is:
onTransactionEnd(function callback)

The parameters are:

finction callback
The callback function to be executed after every transaction ends.

Logging Transaction Data

To tell the MetricsService where to send your transaction data, register a beacon. When a transaction ends, the
MetricsService looks for a registered beacon to send the data.

SEE ALSO:
Adding Performance Marks
Logging Data with Beacons

305
Measuring Performance with MetricsService Adding Performance Marks

Adding Performance Marks

A mark measures a specific event. Use a mark to measure an interval of a larger transaction.

Starting a Mark
To start a mark, use $A.metricsService.markStart(). The syntax is:
markStart(String ns, String name, Object context)

The parameters are:

String ns
Optional. Mark namespace. You can use any value. This parameter doesn't have anything to do with a component's namespace
though you can use the component's namespace as a high-level identifier.
String name
Mark name. You can use any value, such as a component or action's name.
Object context
Optional custom data to log.
To add a mark that doesn't have a separate start and end time, use $A.metricsService.mark().

Ending a Mark
To end a mark, use $A.metricsService.markEnd(). The syntax is:
markEnd(String ns, String name, Object context)

The parameters are:

String ns
Optional. Mark namespace. The value must match the ns value in markStart().
String name
Mark name. The value must match the ns value in markStart().
Object context
Optional custom data to log.

SEE ALSO:
Adding Performance Transactions

Logging Data with Beacons

A beacon is a component that receives the metrics and sends them somewhere for storage. A beacon abstracts the transport layer for
sending collected metrics and transactions.
A beacon must contain a sendData() function that encapsulates all data logging. The beacon markup uses an <aura:method>
tag with id and transaction attributes to define the sendData() function. For example:
<aura:method name="sendData">
<aura:attribute name="id" type="Object" />

306
Measuring Performance with MetricsService Abstracting Measurement with Plugins

<aura:attribute name="transaction" type="Object" />

</aura:method>

The sendData() function can contain any custom logic to log the performance data. Typically, it calls a server-side caboose action
to log the data.
To register a beacon for all transactions, add this JavaScript code:
$A.metricsService.registerBeacon(component);

The init handler for a component is a typical place to register a beacon.

SEE ALSO:
Adding Performance Transactions
aura:method
Calling a Server-Side Action
Caboose Actions
Invoking Actions on Component Initialization

Abstracting Measurement with Plugins

A plugin hooks into the code being measured and enables you to instrument your functional code without adding performance marks
directly in your functional code. Add the performance marks in the plugin so that your functional code doesn't get littered with marks.
This leads to a clean separation between functional code and instrumentation code that measures the performance of the functional
code.
A plugin uses AOP (aspect-oriented programming) and the MetricsService API calls to hook into the code being measured.
Create a plugin when you want to test the performance of your code without adding marks in the functional code. The framework has
several plugins for performance testing of different features. The plugins can be disabled in PROD mode so that the instrumentation
doesn’t adversely affect performance.

Tip: Your plugin code runs on every call to an instrumented function. Be selective in using plugins in PROD mode to limit the
instrumentation to the metrics you care about.
You don't have to create your own plugins unless you want to instrument a complex code path. Alternatively, consider adding a plugin
if you don't have write access to the underlying code that you want to measure, or if the code is called from multiple places and you
don't want to add marks in all those places.
These are the most important methods that you can customize for your plugin.
initialize
Called by MetricsService before bootstrapping the framework so you can bind your before and after hooks using the
instrument() method of MetricsService.
enable
Enables the plugin.
disable
Disables the plugin.
postProcess
The method called before sending the transaction in DEV mode. Add logic to massage the payload that the transaction aggregates.

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Measuring Performance with MetricsService End-to-End MetricsService Example

Tip: The best way to understand plugins is to look at some existing code. For an example of a plugin, see
ClientServiceMetricsPlugin.js in the open source git repo.
The plugin uses $A.metricsService.registerPlugin() to register itself.
// Register the plugin
$A.metricsService.registerPlugin({
"name" : ClientServiceMetricsPlugin.NAME,
"plugin" : ClientServiceMetricsPlugin
});

You can add a plugin in any file as long as it calls $A.metricsService.registerPlugin().

SEE ALSO:
Adding Performance Marks

End-to-End MetricsService Example

Let's tie it all together by creating a beacon and a sample component that creates a transaction and a mark. These metrics are sent to
the beacon.

IN THIS SECTION:
Step 1: Create a Beacon Component
Add a beacon component that receives the metrics data.
Step 2: Add a Transaction and Mark
Add a component that contains a transaction and a mark.

Step 1: Create a Beacon Component

Add a beacon component that receives the metrics data.
1. Add the markup for the beacon.
<!--c:metricsBeacon-->
<aura:component>
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

<aura:method name="sendData">
<aura:attribute name="id" type="Object"/>
<aura:attribute name="transaction" type="Object"/>
</aura:method>
</aura:component>

The component doesn't have any UI output. It just sets up the sendData method for the beacon.

2. Add the client-side controller code.

/*metricsBeaconController.js*/
({
doInit : function(component, event, helper) {
$A.metricsService.registerBeacon(component);

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Measuring Performance with MetricsService Step 2: Add a Transaction and Mark

},

sendData: function (cmp, event, helper) {

var args = event.getParams().arguments;

// Log to console as an example.

// In production-quality code, data would be logged
// and persisted with a caboose server-side action
console.log("in beacon: ", args);
}
})

The doInit() function registers the beacon. The init event configured in the beacon's markup triggers doInit().
This simple beacon logs the output but in production-quality code, you could persist the performance data for analysis.

SEE ALSO:
Logging Data with Beacons

Step 2: Add a Transaction and Mark

Add a component that contains a transaction and a mark.
1. Add the component markup.
<!--c:metricsSample-->
<aura:component>
<c:metricsBeacon/>
<ui:button label="Log Transaction" press="{!c.logTrans}"/>
</aura:component>

The markup includes a reference to the beacon component so that the beacon is loaded.
When you click the button, it will log a transaction after we set up the client-side controller.
2. Add the client-side controller code.
/*metricsSampleController.js*/
({
logTrans : function(cmp) {
console.log("in logTrans");

$A.metricsService.transactionStart('c', 'sampleTrans',
{context : Date.now()}
);
// imagine a server call here

$A.metricsService.markStart('c', 'sampleMark');
// imagine some client-side component creation here
$A.metricsService.markEnd('c', 'sampleMark');

$A.metricsService.transactionEnd('c', 'sampleTrans');
}
})

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Measuring Performance with MetricsService Step 2: Add a Transaction and Mark

The client-side controller creates a transaction and mark. This sample demonstrates the scaffolding and doesn't include
production-quality code that would make a server call and perform some client-side processing. Adding a mark within the transaction
can give you more insight into where time is consumed in a transaction.

3. Click the Log Transaction button in c:metricsSample.

Look in the browser’s console log for the metrics.

SEE ALSO:
Adding Performance Transactions
Adding Performance Marks

310
CUSTOMIZING AURA

CHAPTER 11 Plugging in Custom Code with Adapters

In this chapter ... Aura has a set of adapters that provide default implementations of functionality that you can override.
For example, the localization adapter provides the default behavior for working with labels and locales.
• Default Adapters
You may want to override this behavior for your own localization requirements.
• Overriding Default
Adapters Think of an adapter as a plugin point for your custom code. It's useful to contrast this with the Aura
Integration Service, which enables you to inject Aura components into a Web app that is not developed
in Aura.
AuraAdapter is the base marker interface for all adapters. You can find all the adapter interfaces in
the org.auraframework.adapter package.

SEE ALSO:
Default Adapters
Overriding Default Adapters
Accessing Components from Non-Aura Containers

311
Plugging in Custom Code with Adapters Default Adapters

Default Adapters
Aura has a set of default adapters.

Adapter Description
ComponentLocationAdapter Provides the default location for storing component source files. The default is to store
components on the filesystem but you could override this to store them in a database.

ConfigAdapter Provides many defaults, including the set of available modes, and the version of the
Aura framework.

ContextAdapter Provides the default context. Every request in Aura is associated with a context. After
initial loading of an app, each subsequent request is an XHR POST that contains your
Aura context configuration, which includes the mode to run in, the name of the app,
and the namespaces that already have metadata loaded on the client.

ExceptionAdapter Provides the default exception handling. The default is to log the exception.

ExpressionAdapter Provides the default expression language.

FormatAdapter Provides the default implementations for reading and writing different resources, such
as Aura markup, CSS, or JSON.

GlobalValueProviderAdapter Provides the global value providers. Global value providers are global values, such as
$Label, that a component can use in expressions.

JsonSerializerAdapter Provides the default JSON serializers. You can use this adapter to customize how Aura
locates the correct serializer implementation to marshall objects to and from JSON.

LocalizationAdapter Provides the default label and locale handling.

LoggingAdapter Provides the default logging.

PrefixDefaultsAdapter Provides the default prefixes for Aura definitions. Each definition describes metadata
for an element, such as a component, event, controller, or model.

RegistryAdapter Provides the default registries. Registries store metadata definitions. Some registries
last for the duration of a request, while others are cached for the lifetime of an app.

StyleAdapter Provides the default CSS themes.

SEE ALSO:
Plugging in Custom Code with Adapters
Overriding Default Adapters

Overriding Default Adapters

There are several ways to override the default adapters.
To override one of the default adapters:
1. Extend an existing adapter or create a new class that implements the adapter interface that you're overriding.

312
Plugging in Custom Code with Adapters Overriding Default Adapters

2. Use the @Override annotation on each interface method that you implement.

SEE ALSO:
Plugging in Custom Code with Adapters
Default Adapters
Customizing your Label Implementation

313
CHAPTER 12 Accessing Components from Non-Aura Containers
In this chapter ... The Aura Integration Service enables plugging Aura components into non-Aura HTML containers.
Because Aura requires an app to start and to render components, the Aura Integration Service creates
• Add an Aura button
inside an HTML div
and manages an internal integration app on your behalf for the components you're embedding. This
container makes it easy to use Aura components in an HTML-based application.
Also, the Aura Integration Service allows partial page updates. You can add additional components to
a page that has already been loaded and after an app has already been created.
An Aura component instance is embedded in a page inside a script tag and is bound to its parent DOM
element.
The Aura Integration Service provides a set of Java APIs that allow you to embed a component. The Java
APIs are included in the following interfaces and their class implementations.
• IntegrationService Interface (implemented by IntegrationServiceImpl): Enables the
creation of an integration using the createIntegration() method.
• Integration Interface (implemented by IntegrationImpl): Enables adding components using
the injectComponent() method.

Note: The Aura History Service and Aura Layout Service are not supported with the Aura Integration
Service, and hence embedded components can't make use of these services.

SEE ALSO:
Customizing Behavior with Modes
Component IDs

314
Accessing Components from Non-Aura Containers Add an Aura button inside an HTML div container

Add an Aura button inside an HTML div container

The Aura Integration Service enables you to plug Aura components into HTML containers.
1. Create a Java instance of the Aura Integration Service.
IntegrationService svc = Aura.getIntegrationService();

2. Create an integration, which enables you to embed components in your page.

• For the first argument, pass the context path. For servlets in the default root context, it is an empty string.
• For the second argument, pass the mode. In this example, we're specifying the DEV mode.
• For the third argument, pass a Boolean value to indicate whether Aura should create an integration app or not. In this case, we're
passing true. If you want to perform a partial page update, pass false for the third argument. This enables you to add more
components after a page has been loaded and an app has already been created.
Integration integ = svc.createIntegration("", Mode.DEV, true);

3. Call the injectComponent method to embed a component in a parent container.

• For the first argument, pass the component's fully qualified name. In this case, it is "ui:button".
• For the second argument, pass the component's attributes as a map. This example creates a map with one attribute and passes
it as the second argument.
• For the third argument, pass the local component ID. In this example, it is "button1".
• For the fourth argument, pass the DOM identifier for the parent container element. In this example, it is "div1".
• For the fifth argument, pass a buffer that will contain the script output.
• For the sixth argument, pass a boolean set to true to use asynchronous component creation for the injected component
instead of the default method of printing the component HTML to the page. The asynchronous option is more performant if
you are injecting multiple components.
Map<String, Object> attributes = Maps.newHashMap();
attributes.put("label", "Click Me");
Appendable out = new StringBuffer();
boolean async = true;
integration.injectComponent("ui:button", attributes, "button1", "div1", out, async);

Example: This is the full listing of the sample.

IntegrationService svc = Aura.getIntegrationService();
Integration integration = svc.createIntegration("", Mode.DEV, true);
Map<String, Object> attributes = Maps.newHashMap();
attributes.put("label", "Click Me");
Appendable out = new StringBuffer();
boolean async = true;
integration.injectComponent("ui:button", attributes, "button1", "div1", out, async);

315
CHAPTER 13 Customizing Data Type Conversions
In this chapter ... A custom converter enables the conversion of one Java type to another Java type for client data sent to
the server or for server markup data.
• Registering Custom
Converters
When a client calls a server-side controller action, data that the client sends, such as input parameters
for a server action, is sent in JSON format. The JSON representation of data is converted to target Java
• Custom Converters
types on the server. Similarly, values in Aura markup on the server, such as component attribute values,
are evaluated as Java strings. These strings are converted to corresponding Java types. For primitive Java
types, the type conversion is implicit and doesn't require the addition of any converters. For example, a
JSON string is converted to a Java string, and a JSON list is converted to a Java ArrayList. For custom
types, or when there is no one-to-one mapping between the source value and the target type, Aura
calls the custom converter that you provide to create an instance of the custom Java type corresponding
to the JSON representation on the client or the markup attribute value on the server.
An example of a custom converter is a converter used to convert comma-delimited string values to an
ArrayList. A component attribute of type List can have a default value in markup of a comma-delimited
string of values. Aura converts this attribute string value into an ArrayList by calling the custom String
to ArrayList converter.

SEE ALSO:
Custom Java Class Types
Creating Server-Side Logic with Controllers
Supported aura:attribute Types

316
Customizing Data Type Conversions Registering Custom Converters

Registering Custom Converters

Register a custom converter to enable conversion of one Java type to another Java type when sending data to and from the server.
To register a custom converter:
1. Create a class that implements the Converter interface. Add implements Converter<Type1, Type2> at the end
of the first line of your class definition, after the class name. Replace Type1 with the original Java type and Type2 with the target
Java type. Next, implement each method in the Converter interface. For better readability of your code, we recommend you
name the class using the format Type1ToType2Converter. This is an example of a skeletal class implementing the
Converter interface. Type1 and Type2 are placeholders for the Java original type and the converted type, respectively.

public class Type1ToType2Converter implements Converter<Type1, Type2> {

@Override
public Type2 convert(Type1 value) {
// Convert value into a value of Type2 and return it.
// Return converted value.
}

@Override
public Class<Type1> getFrom() {
// return Type1.class;
}

@Override
public Class<Type2> getTo() {
// return Type2.class;
}

@Override
public Class<?>[] getToParameters() {
// Return the types contained in the custom type.
}

2. Create another class annotated with @AuraConfiguration. The class must be in the configuration package.
3. Add a public static method to this class annotated with @Impl. The method should return either the Converter<?,
?> type or Converter<Type1, Type2> with the actual original and target Java types. The method returns a new instance
of the class you created earlier, which implements the Converter interface.
package configuration;

@AuraConfiguration
public class MyTypeConverterConfig {
@Impl
public static Converter<Type1, Type2> exampleTypeConverter() {
return new Type1ToType2Converter();
}
}

4. To specify additional conversions, repeat the previous steps. Each new conversion requires a converter implementation class and
the addition of a corresponding method to the Aura configuration class.

317
Customizing Data Type Conversions Custom Converters

Custom Converters
Here are a few examples of custom converters.

Example 1: Custom Type Conversion for a Component Attribute

This example shows how to add a converter to convert an attribute string value to the corresponding custom type. It contains the
definition of the custom type, MyCustomType, an example of the attribute, the corresponding converter, and a method in the Aura
configuration class.
This is the definition of the custom type, MyCustomType.
package doc.sample;

public class MyCustomType implements JsonSerializable {

private String val;

public MyCustomType(String val) {

this.val = val;
}

@Override
public void serialize(Json json) throws IOException {
json.writeString(val);
}
}

This is the attribute of type MyCustomType with a default value of "x".

<aura:attribute name="myObj" type="java://doc.sample.MyCustomType" default="x"/>

This is the converter implementation for converting a string (the attribute value) to an object of type MyCustomType (the target Java
type).
public class StringToMyCustomTypeConverter implements Converter<String, MyCustomType> {

@Override
public MyCustomType convert(String value) {
return new MyCustomType(value);
}

@Override
public Class<String> getFrom() {
return String.class;
}

@Override
public Class<MyCustomType> getTo() {
return MyCustomType.class;
}

@Override
public Class<?>[] getToParameters() {
return null;

318
Customizing Data Type Conversions Custom Converters

This is the corresponding Aura Configuration method.

package configuration;

@AuraConfiguration
public class MyCustomTypeConverterConfig {
@Impl
public static Converter<String, MyCustomType> exampleTypeConverter() {
return new StringToMyCustomTypeConverter();
}
}

Example 2: Parameterized Type Conversion for a Server Action Call

This example shows how to add a converter to convert the type of a parameter passed to a server-side controller action call that a client
makes. The target type of the conversion is a parameterized type, List<MyCustomType>, which is a list of MyCustomType
objects.
This example is based on the MyCustomType class defined earlier.
This is the client call to the accept action on the server-side controller. The client passes an array of three string values that corresponds
to a list of MyCustomType objects. Because the parameter value is an array of objects, the original type of the conversion is ArrayList.
custom : function(c) {
var a = c.get("c.accept");
a.setParams({myObjs:["x","y","z"]});
$A.enqueueAction(a);
},

This is how the accept method looks in the server-side controller. Notice the parameter of the accept method is of type
List<MyCustomType>. This is the target type of the conversion.

@AuraEnabled
public static void accept(@Key("myObjs") List<MyCustomType> myObjs) {
for (MyCustomType obj : myObjs) {
System.err.println("MyCustomType:" + obj);
}
}

This is the converter implementation that converts an ArrayList (the parameter array sent by the client) to a List of MyCustomType
objects on the server.
public class ArrayListToMyCustomTypeListConverter implements Converter<ArrayList, List> {

@Override
public List<MyCustomType> convert(ArrayList value) {
List<MyCustomType> retList = Lists.newLinkedList();
for (Object part : value) {
retList.add(new MyCustomType(part.toString()));
}

319
Customizing Data Type Conversions Custom Converters

return retList;
}

@Override
public Class<ArrayList> getFrom() {
return ArrayList.class;
}

@Override
public Class<List> getTo() {
return List.class;
}

@Override
public Class<?>[] getToParameters() {
return new Class[] { MyCustomType.class };
}
}

This is the corresponding Aura Configuration method.

package configuration;

@AuraConfiguration
public class MyCustomTypeListConverterConfig {
@Impl
public static Converter<ArrayList, List<MyCustomType>> exampleTypeConverter() {
return new ArrayListToList<MyCustomType>Converter();
}
}

Example 3: Parameterized Type Conversion for a Component Attribute

This example is similar to the previous one except that the conversion is done for an attribute value. In this example, consider the following
attribute that holds a list of MyCustomType objects and with a default value of "x,y,z". Because the attribute value is a string,
the original type of the conversion is String. The target type is List<MyCustomType>.
This example is based on the MyCustomType class defined earlier.
<aura:attribute name="myObjs" type="java://java.util.List<doc.sample.MyCustomType>"
default="x,y,z"/>

This is the converter implementation for converting a string to a list of MyCustomType objects.
public class StringToMyCustomTypeListConverter implements Converter<String, List> {

@Override
public List<MyCustomType> convert(String value) {
List<MyCustomType> retList = Lists.newLinkedList();
for (String part : AuraTextUtil.splitSimple(",", value)) {
retList.add(new MyCustomType(part));
}
return retList;
}

320
Customizing Data Type Conversions Custom Converters

@Override
public Class<String> getFrom() {
return String.class;
}

@Override
public Class<List> getTo() {
return List.class;
}

@Override
public Class<?>[] getToParameters() {
return new Class[] { MyCustomType.class };
}
}

This is the corresponding Aura Configuration method.

package configuration;

@AuraConfiguration
public class MyCustomTypeList2ConverterConfig {
@Impl
public static Converter<String, List<MyCustomType>> exampleTypeConverter() {
return new StringToList<MyCustomType>Converter();
}
}

321
CHAPTER 14 Reference
In this chapter ... This section contains reference documentation including details of the various tags available in the
framework.
• Reference Doc App
• Supported
aura:attribute Types
• aura:application
• aura:component
• aura:clientLibrary
• aura:dependency
• aura:event
• aura:if
• aura:interface
• aura:iteration
• aura:method
• aura:renderIf
• aura:set
• Messaging
Component
Reference
• System Event
Reference
• Supported HTML
Tags

322
Reference Reference Doc App

Reference Doc App

The Reference tab of the doc app includes more reference information, including descriptions and source for the out-of-the-box
components that come with the framework, as well as the JavaScript API.

Supported aura:attribute Types

aura:attribute describes an attribute available on an app, interface, component, or event.

Attribute Name Type Description

access String Indicates whether the attribute can be used outside of its own namespace.
Possible values are internal (default), private, public, and
global.

name String Required. The name of the attribute. For example, if you set
<aura:attribute name="isTrue" type="Boolean" />
on a component called aura:newCmp, you can set this attribute when you
instantiate the component; for example,<aura:newCmp
isTrue="false" />.

type String Required. The type of the attribute. For a list of basic types supported, see Basic
Types.

default String The default value for the attribute, which can be overwritten as needed. When
setting a default value, expressions using the $Label, $Locale, and
$Browser global value providers are supported. Alternatively, to set a
dynamic default, use an init event. See Invoking Actions on Component
Initialization on page 151.

required Boolean Determines if the attribute is required. The default is false.

description String A summary of the attribute and its usage.

serializeTo String For optimization. Determines if the attribute is transported from server to client
or from client to server. Attributes are transported in JSON format. Valid values
are SERVER, BOTH, or NONE. The default is BOTH.
Specify SERVER if you don't want to serialize the attribute to the client.
Specify NONE if you don't need the attribute to be serialized at all. For example,
use NONE if it's a client-side only attribute. If you have a JavaScript object
array that must be accessible to markup but don't have a requirement on how
the objects are constructed, you can use <aura:attribute
name="myObj" type="List" serializeTo="NONE">.

All <aura:attribute> tags have name and type values. For example:
<aura:attribute name="whom" type="String" />

323
Reference Basic Types

Note: Although type values are case insensitive, case sensitivity should be respected as your markup interacts with JavaScript,
CSS, and Java.

SEE ALSO:
Component Attributes

Basic Types
Here are the supported basic type values. Some of these types correspond to the wrapper objects for primitives in Java. Since the
framework is written in Java, defaults, such as maximum size for a number, for these basic types are defined by the Java objects that
they map to.

type Example Description

Boolean <aura:attribute Valid values are true or false. To set a default value
name="showDetail" of true, add default="true".
type="Boolean" />

Date <aura:attribute A date corresponding to a calendar day in the format

name="startDate" type="Date" yyyy-mm-dd. The hh:mm:ss portion of the date is not stored.
/> To include time fields, use DateTime instead.

DateTime <aura:attribute A date corresponding to a timestamp. It includes date and

name="lastModifiedDate" time details with millisecond precision.
type="DateTime" />

Decimal <aura:attribute Decimal values can contain fractional portions (digits to

name="totalPrice" the right of the decimal). Maps to java.math.BigDecimal.
type="Decimal" /> Decimal is better than Double for maintaining
precision for floating-point calculations. It’s preferable for
currency fields.

Double <aura:attribute Double values can contain fractional portions. Maps to

name="widthInchesFractional" java.lang.Double. Use Decimal for currency fields instead.
type="Double" />

Integer <aura:attribute Integer values can contain numbers with no fractional

name="numRecords" portion. Maps to java.lang.Integer, which defines its limits,
type="Integer" /> such as maximum size.

Long <aura:attribute Long values can contain numbers with no fractional

name="numSwissBankAccount" portion. Maps to java.lang.Long, which defines its limits,
type="Long" /> such as maximum size.
Use this data type when you need a range of values wider
than those provided by Integer.

String <aura:attribute name="message" A sequence of characters.

type="String" />

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Reference Function Type

You can use arrays for each of these basic types. For example:
<aura:attribute name="favoriteColors" type="String[]" default="['red','green','blue']" />

To retrieve a string array from your Java controller, use List<String>.

public List<String> getStringList() {
List<String> colors = new List<>();
colors.add("red");
colors.add("blue");
return colors;
}

Function Type
An attribute can have a type corresponding to a JavaScript function.
<aura:attribute name="callback" type="Function" />

For an example, see Return Result for Asynchronous Code.

Object Types
An attribute can have a type corresponding to an Object.
<aura:attribute name="data" type="Object" />

For example, you may want to create an attribute of type Object to pass a JavaScript array as an event parameter. In the component
event, declare the event parameter using aura:attribute.
<aura:event type="COMPONENT">
<aura:attribute name="arrayAsObject" type="Object" />
<aura:event>

In JavaScript code, you can set the attribute of type Object.

// Set the event parameters
var event = component.getEvent(eventType);
event.setParams({
arrayAsObject:["file1", "file2", "file3"]
});
event.fire();

Checking for Types

To determine a variable type, use typeof or a standard JavaScript method instead. The instanceof operator is unreliable due to
the potential presence of multiple windows or frames.

Collection Types
Here are the supported collection type values.

325
Reference Collection Types

type Example Description

type[] (Array) <aura:attribute An array of items of a defined type.
name="colorPalette"
type="String[]" default="['red',
'green', 'blue']" />

List <aura:attribute An ordered collection of items.

name="colorPalette" type="List"
default="['red', 'green',
'blue']" />

Map <aura:attribute A collection that maps keys to values. A map can’t

name="sectionLabels" type="Map" contain duplicate keys. Each key can map to at
default="{ a: 'label1', b: most one value. Defaults to an empty object, {}.
'label2' }" /> Retrieve values by using
cmp.get("v.sectionLabels")['a'].

Set <aura:attribute name="collection" A collection that contains no duplicate elements.

type="Set" default="['red', The order for set items is not guaranteed. For
'green', 'blue']" /> example, "red,green,blue" might be
returned as "blue,green,red".

Checking for Types

To determine a variable type, use typeof or a standard JavaScript method, such as Array.isArray(), instead. The instanceof
operator is unreliable due to the potential presence of multiple windows or frames.

Setting List Items

There are several ways to set items in a list. To use a client-side controller, create an attribute of type List and set the items using
component.set().
This example retrieves a list of numbers from a client-side controller when a button is clicked.
<aura:attribute name="numbers" type="List"/>
<lightning:button onclick="{!c.getNumbers}" label="Display Numbers" />
<aura:iteration var="num" items="{!v.numbers}">
{!num.value}
</aura:iteration>

/** Client-side Controller **/

({
getNumbers: function(component, event, helper) {
var numbers = [];
for (var i = 0; i < 20; i++) {
numbers.push({
value: i
});
}
component.set("v.numbers", numbers);

326
Reference Custom Java Class Types

}
})

To retrieve list data from a model, use aura:iteration. This example retrieves data from a model, assuming that you have set the
model attribute on the aura:component tag.

<aura:attribute name="sizes" type="List"/>

<aura:iteration items="{!m.sizes}" var="size">
{!size.value}
</aura:iteration>

/** Server-side Model **/

@Model
public class MyModel {
public List<MyDataType> getSizes() {
ArrayList<MyDataType> s = new ArrayList<MyDataType>(2);
//Set list items here
return s;
}
}

Setting Map Items

To add a key and value pair to a map, use the syntax myMap['myNewKey'] = myNewValue.
var myMap = cmp.get("v.sectionLabels");
myMap['c'] = 'label3';

The following example retrieves data from a map.

for (var key in myMap){
//do something
}

SEE ALSO:
Java Models
Custom Java Class Types

Custom Java Class Types

An attribute can have a type corresponding to a Java class. For example, this is an attribute for a Color Java class:
<aura:attribute name="color" type="java://org.docsample.Color" />

If you create a custom Java type, it must implement JsonSerializable to enable marshalling from the server to the client.

Support for Collections

If an <aura:attribute> can contain more than one element, use a List instead of an array.

Note: You can't declare an <aura:attribute> to be an array of a custom Java type.

327
Reference Framework-Specific Types

The following aura:attribute shows the syntax for a List of Java objects:
<aura:attribute name="colorPalette" type="List" />

You can also use type="java://List" instead of type="List". Both definitions are functionally equivalent.
<aura:attribute name="colorPalette" type="java://List" />

Framework-Specific Types
Here are the supported type values that are specific to the framework.

type Example Description

Aura.Component N/A A single component. We recommend using
Aura.Component[] instead.

Aura.Component[] <aura:attribute Use this type to set blocks of markup. An

name="detail" attribute of type Aura.Component[]
type="Aura.Component[]"/> is called a facet.
To set a default value for
type="Aura.Component[]", put
the default markup in the body of
aura:attribute. For example:

<aura:component>
<aura:attribute
name="detail"
type="Aura.Component[]">
<p>default
paragraph1</p>
</aura:attribute>
Default value is:
{!v.detail}
</aura:component>

Aura.Action <aura:attribute Use this type to pass an action to a

name="onclick" component. See Using the Aura.Action
type="Aura.Action"/> Attribute Type.

SEE ALSO:
Component Body
Component Facets

Using the Aura.Action Attribute Type

An Aura.Action is a reference to an action in the framework. If a child component has an Aura.Action attribute, a parent
component can pass in an action handler when it instantiates the child component in its markup. This pattern is a shortcut to pass a
controller action from a parent component to a child component that it contains, and is used for on* handlers, such as onclick.

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Reference aura:application

Warning: Although Aura.Action works for passing an action handler to a child component, we recommend registering an
event in the child component and firing the event in the child’s controller instead. Then, handle the event in the parent component.
The event approach requires a few extra steps in creating or choosing an event and firing it but events are the standard way to
communicate between components.
Aura.Action shouldn’t be used for other use cases. Here are some known limitations of Aura.Action.
• Don’t use cmp.set() in JavaScript code to reset an attribute of type="Aura.Action" after it’s previously been set.
Doing so generates an error.
Unable to set value for key 'c.passedAction'. Value provider does not implement
'set(key, value)'. : false

• Don’t use $A.enqueueAction() in the child component to enqueue the action passed to the Aura.Action attribute.

Example
This example demonstrates how to pass an action handler from a parent component to a child component.
Here’s the child component with the Aura.Action attribute. The onclick handler for the button uses the value of the onclick
attribute, which has type of Aura.Action.
<!-- child.cmp -->
<aura:component>
<aura:attribute name="onclick" type="Aura.Action"/>

<p>Child component with Aura.Action attribute</p>

<lightning:button label="Execute the passed action" onclick="{!v.onclick}"/>
</aura:component>

Here’s the parent component that contains the child component in its markup.
<!-- parent.cmp -->
<aura:component>
<p>Parent component passes handler action to c:child</p>
<c:child onclick="{!c.parentAction}"/>
</aura:component>

When you click the button in c:child, the parentAction action in the controller of c:parent is executed.
Instead of an Aura.Action attribute, you could use <aura:registerEvent> to register an onclick event in the child
component. You’d have to define the event and create an action in the child’s controller to fire the event. This event-based approach
requires a few extra steps but it’s more in line with standard practices for communicating between components.

SEE ALSO:
Framework-Specific Types
Handling Events with Client-Side Controllers

aura:application
An app is a special top-level component whose markup is in a .app file.
The markup looks similar to HTML and can contain components as well as a set of supported HTML tags. The .app file is a standalone
entry point for the app and enables you to define the overall application layout, style sheets, and global JavaScript includes. It starts with

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Reference aura:application

the top-level <aura:application> tag, which contains optional system attributes. These system attributes tell the framework
how to configure the app.

System Attribute Type Description

access String Indicates whether the app can be extended by another app outside of a namespace.
Possible values are internal (default), public, and global.

controller String The server-side controller class for the app. The format is
java://<package.class>.

description String A brief description of the app.

extends Component The app to be extended, if applicable. For example,

extends="namespace:yourApp".

extensible Boolean Indicates whether the app is extensible by another app. Defaults to false.

implements String A comma-separated list of interfaces that the app implements.

locationChangeEvent Event The framework monitors the location of the current window for changes. If the #
value in a URL changes, the framework fires an application event. The
locationChangeEvent defines this event. The default value is
aura:locationChange. The locationChange event has a single
attribute called token, which is set with everything after the # value in the URL.

model String The model class used to initialize data for the app. The format is
java://<package.class>.

preload String Deprecated. Use the aura:dependency tag instead.

If you use the preload system attribute, the framework internally converts the
value to <aura:dependency> tags.

render String Renders the component using client-side or server-side renderers. If not provided,
the framework determines any dependencies and whether the application should
be rendered client-side or server-side.
Valid options are client or server. The default is auto.
For example, specify render="client" if you want to inspect the application
on the client-side during testing.

renderer String Only use this system attribute if you want to use a custom client-side or server-side
renderer. If you don't set a renderer, the framework uses its default rendering,
which is sufficient for most use cases. If you don't define this system attribute, your
application is autowired to a client-side renderer named
<appName>Renderer.js, if it exists in your application bundle.

template Component The name of the template used to bootstrap the loading of the framework and
the app. The default value is aura:template. You can customize the template
by creating your own component that extends the default template. For example:
<aura:component extends="aura:template" ... >

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Reference aura:component

System Attribute Type Description

tokens String A comma-separated list of tokens bundles for the application. For example,
tokens="ns:myAppTokens". Tokens make it easy to ensure that your
design is consistent, and even easier to update it as your design evolves. Define
the token values once and reuse them throughout your application.

useAppcache Boolean Deprecated. Browser vendors have deprecated AppCache, so we followed their
lead. Remove the useAppcache attribute in the <aura:application>
tag of your standalone apps (.app files) to avoid cross-browser support issues
due to deprecation by browser vendors.
If you don’t currently set useAppcache in an <aura:application> tag,
you don’t have to do anything because the default value of useAppcache is
false.

aura:application also includes a body attribute defined in a <aura:attribute> tag. Attributes usually control the output
or behavior of a component, but not the configuration information in system attributes.

Attribute Type Description

body Component[] The body of the app. In markup, this is
everything in the body of the tag.

SEE ALSO:
URL-Centric Navigation
Creating Apps
Using the AppCache
Application Access Control

aura:component
The root of the component hierarchy. Provides a default rendering implementation.
Components are the functional units of Aura, which encapsulate modular and reusable sections of UI. They can contain other components
or HTML markup. The public parts of a component are its attributes and events. Aura provides out-of-the-box components in the aura
and ui namespaces.
Every component is part of a namespace. For example, the button component is saved as button.cmp in the ui namespace
can be referenced in another component with the syntax <ui:button label="Submit"/>, where label="Submit" is
an attribute setting.
To create a component, follow this syntax.
<aura:component>
<!-- Optional coponent attributes here -->
<!-- Optional HTML markup -->
<div class="container">
Hello world!

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Reference aura:component

<!-- Other components -->

</div>
</aura:component>

A component has the following optional attributes.

Attribute Type Description

abstract Boolean Set to true if the component is abstract. The default is false.

access String Indicates whether the component can be used outside of its own
namespace. Possible values are internal (default), public,
and global.

aura:flavorable Boolean Set to true if the component is flavorable. The default is false.

controller String The server-side controller class for the component. The format is
java://<package.class>.

defaultFlavor String The comma-separated list of flavor names in the component bundle,
defined in the <componentName>Flavors.css file.

description String A description of the component.

extends Component The component to be extended.

extensible Boolean Set to true if the component can be extended. The default is
false.

helper String The external JavaScript helper file to use. If you use an external helper
file, the helper methods in your component bundle will not be
accessible. The format is js://namespace.component.

implements String A comma-separated list of interfaces that the component implements.

isTemplate Boolean Set to true if the component is a template. The default is false.
A template must have isTemplate="true" set in its
<aura:component> tag.

<aura:component isTemplate="true"
extends="aura:template">

model String The model class used to initialize data for the component. The format
is java://<package.class>.

provider String The JavaScript or Java provider, in the format

java://<package.class> or
js://namespace.component. A provider enables you to use
an abstract component in markup. Defining a server-side provider
overrides any client-side provider in the component bundle.

render String Renders the component using client-side or server-side renderers. If

not provided, the framework determines any dependencies and
whether the component should be rendered client- or server-side.
Valid options are client or server. The default is auto.

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Reference aura:clientLibrary

Attribute Type Description

Specify this attribute in the top-level component. For example, specify
render="client" if you want to inspect the component on
the client-side during testing.

support String The support level for the component. Valid options are PROTO,
DEPRECATED, BETA, or GA.

template Component The template for this component. A template bootstraps loading of
the framework and app. The default template is aura:template.
You can customize the template by creating your own component
that extends the default template. For example:
<aura:component extends="aura:template" ...
>

whitespace String Preserves or removes unnecessary whitespace in the component

markup. Valid options are preserve or optimize. The default
is optimize.

aura:component includes a body attribute defined in a <aura:attribute> tag. Attributes usually control the output or
behavior of a component, but not the configuration information in system attributes.

Attribute Type Description

body Component[] The body of the component. In markup, this
is everything in the body of the tag.

aura:clientLibrary
The <aura:clientLibrary> tag enables you to use JavaScript or CSS libraries. Use the tag in a .cmp or .app resource.
The <aura:clientLibrary> tag includes these system attributes.

System Attribute Description

modes A comma-separated list of modes that use the client library. If no value is set, the library is available
for all modes.

name The name of the library. Use this name when you load the library in JavaScript code by calling
$A.clientService.loadClientLibrary(libName, callback).

prefetch Specifies whether browsers should download the script to browser cache during idle time. This
prefetching can improve app performance by reducing the loading time for scripts.
Defaults to true. If your component doesn’t always use the script, set prefetch to false
and load the library when you need it.

Note: The prefetch request isn’t guaranteed. Prefetching only works for JavaScript libraries
and browsers that support the <link rel="prefetch" ... /> hint.

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Reference aura:dependency

System Attribute Description

type The type of library. Values are CSS, or JS for JavaScript.

Use the Library

The <aura:clientLibrary> tag in markup registers a library for a component or application. For example:
<aura:clientLibrary name="libraryName" />

To use the library, you must call this method in JavaScript code.
$A.clientService.loadClientLibrary(libName, callback)

If the library hasn’t previously been loaded on the client, this method loads the library. If the prefetch attribute is set to true, the
library can be loaded from browser cache, which avoids an extra server trip and reduces the latency of script loading.
This example shows how to use a library in JavaScript code.
$A.clientService.loadClientLibrary("libraryName",
function() {
// use the library
}
);

The first argument matches the name attribute used for the library in the <aura:clientLibrary> tag in markup.
<aura:clientLibrary name="libraryName" />

The second argument is the callback function that uses the library after it’s loaded.

SEE ALSO:
Styling Apps
Using External JavaScript Libraries

aura:dependency
The <aura:dependency> tag enables you to declare dependencies, which improves their discoverability by the framework.
The framework automatically tracks dependencies between definitions, such as components, defined in markup. This enables the
framework to send the definitions to the browser. However, if a component’s JavaScript code dynamically instantiates another component
or fires an event that isn’t directly referenced in the component’s markup, use <aura:dependency> in the component’s markup
to explicitly tell the framework about the dependency. Similarly, add a dependency for resources created in client- or server-side providers.
Adding the <aura:dependency> tag ensures that a definition, such as a component, and its dependencies are sent to the client,
when needed.
For example, adding this tag to a component marks the sampleNamespace:sampleComponent component as a dependency.
<aura:dependency resource="markup://sampleNamespace:sampleComponent" />

Add this tag to component markup to mark the event as a dependency.

<aura:dependency resource="markup://sampleNamespace:sampleEvent" type="EVENT"/>

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Reference aura:event

Use the <aura:dependency> tag if you fire an event in JavaScript code and you’re not registering the event in component markup
using <aura:registerEvent>. Using an <aura:registerEvent> tag is the preferred approach.
The <aura:dependency> tag includes these system attributes.

System Attribute Description

resource The resource that the component depends on, such as a component or event. For example,
resource="markup://sampleNamespace:sampleComponent" refers to the
sampleComponent in the sampleNamespace namespace.

Note: Using an asterisk (*) for wildcard matching is deprecated. Instead, add an
<aura:dependency> tag for each resource that’s not directly referenced in the
component’s markup. Wildcard matching can cause save validation errors when no
resources match. Wildcard matching can also slow page load time because it sends more
definitions than needed to the client.

type The type of resource that the component depends on. The default value is COMPONENT.

Note: Using an asterisk (*) for wildcard matching is deprecated. Instead, add an
<aura:dependency> tag for each resource that’s not directly referenced in the
component’s markup. Be as selective as possible in the types of definitions that you send
to the client.
The most commonly used values are:
• COMPONENT
• EVENT
• INTERFACE
• APPLICATION
Use a comma-separated list for multiple types; for example: COMPONENT,APPLICATION.

SEE ALSO:
Client-Side Runtime Binding of Components
Server-Side Runtime Binding of Components
Dynamically Creating Components
Fire Component Events
Fire Application Events

aura:event
An event is represented by the aura:event tag, which has the following attributes.

Attribute Type Description

access String Indicates whether the event can be extended or used outside of its
own namespace. Possible values are internal (default), public,
and global.

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Reference aura:if

Attribute Type Description

description String A description of the event.

extends Component The event to be extended. For example,

extends="namespace:myEvent".

type String Required. Possible values are COMPONENT or APPLICATION.

support String The support level for the event. Valid options are PROTO,
DEPRECATED, BETA, or GA.

SEE ALSO:
Communicating with Events
Event Access Control

aura:if
aura:if renders the content within the tag if the isTrue attribute evaluates to true.
The framework evaluates the isTrue expression and instantiates components either in its body or else attribute.

Note: aura:if instantiates the components in either its body or the else attribute, but not both. aura:renderIf
instantiates both the components in its body and the else attribute, but only renders one. If the state of isTrue changes,
aura:if has to first instantiate the components for the other state and then render them. We recommend using aura:if
instead of aura:renderIf to improve performance.

Attribute Name Type Description

else ComponentDefRef[] The markup to render when isTrue evaluates to false. Set this attribute using
the aura:set tag.

isTrue string Required. An expression that determines whether the content is displayed. If it
evaluates to true, the content is displayed.

Example
This snippet of markup uses the <aura:if> tag to conditionally display an edit button.
<aura:attribute name="edit" type="Boolean" default="true"/>
<aura:if isTrue="{!v.edit}">
<ui:button label="Edit"/>
<aura:set attribute="else">
You can’t edit this.
</aura:set>
</aura:if>

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Reference aura:interface

If the edit attribute is set to true, a ui:button displays. Otherwise, the text in the else attribute displays.

SEE ALSO:
Best Practices for Conditional Markup
aura:renderIf

aura:interface
The aura:interface tag has the following optional attributes.

Attribute Type Description

access String Indicates whether the interface can be extended or used outside of
its own namespace. Possible values are internal (default),
public, and global.

description String A description of the interface.

extends Component The comma-seperated list of interfaces to be extended. For example,

extends="namespace:intfB".

provider String The provider for the interface.

support String The support level for the interface. Valid options are PROTO,
DEPRECATED, BETA, or GA.

SEE ALSO:
Interfaces
Interface Access Control

aura:iteration
aura:iteration iterates over a collection of items and renders the body of the tag for each item.
Data changes in the collection are rerendered automatically on the page. aura:iteration supports iterations containing components
that have server-side dependencies or that can be created exclusively on the client-side.

Attribute Name Type Description

body ComponentDefRef[] Required. Template to use when creating components for each
iteration. You can put any markup in the body. A
ComponentDefRef[] stores the metadata of the component
instances to create on each iteration, and each instance is then
stored in realbody.

end Integer The index of the collection to stop at (exclusive).

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Reference aura:method

Attribute Name Type Description

forceServer Boolean Force a server request for the component body. Set to true if
the iteration requires any server-side creation. The default is
false.

indexVar String The variable name to use for the index of each item inside the
iteration.

items List Required. The collection of data to iterate over.

realbody Component[] Do not use. Any value set is ignored. Placeholder for body
rendering.

start Integer The index of the collection to start at (inclusive).

var String Required. The variable name to use for each item inside the
iteration.

This example shows how you can use aura:iteration exclusively on the client-side with an HTML meter tag.
<aura:component>
<aura:iteration items="1,2,3,4,5" var="item">
<meter value="{!item / 5}"/><br/>
</aura:iteration>
</aura:component>

The output shows five meters with ascending values of one to five.

SEE ALSO:
Client-Side Runtime Binding of Components
Server-Side Runtime Binding of Components

aura:method
Use <aura:method> to define a method as part of a component's API. This enables you to directly call a method in a component’s
client-side controller instead of firing and handling a component event. Using <aura:method> simplifies the code needed for a
parent component to call a method on a child component that it contains.
The <aura:method> tag has these system attributes.

Attribute Type Description

name String The method name. Use the method name to call the method in
JavaScript code. For example:
cmp.sampleMethod(param1);

action Expression The client-side controller action to execute. For example:

action="{!c.sampleAction}"

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Reference aura:method

Attribute Type Description

sampleAction is an action in the client-side controller. If you
don’t specify an action value, the controller action defaults to
the value of the method name.

access String The access control for the method. Valid values are:
• internal—Any component in a system namespace can call
the method. A system namespace is a privileged namespace
that has access to all components. This is the default access
level.
• public—Any component in the same namespace can call the
method.
• global—Any component in any namespace can call the
method.

description String The method description.

Declaring Parameters
An <aura:method> can optionally include parameters. Use an <aura:attribute> tag within an <aura:method> to
declare a parameter for the method. For example:
<aura:method name="sampleMethod" action="{!c.doAction}"
description="Sample method with parameters">
<aura:attribute name="param1" type="String" default="parameter 1"/>
<aura:attribute name="param2" type="Object" />
</aura:method>

Note: You don’t need an access system attribute in the <aura:attribute> tag for a parameter.

Creating a Handler Action

This handler action shows how to access the arguments passed to the method.
({
doAction : function(cmp, event) {
var params = event.getParam('arguments');
if (params) {
var param1 = params.param1;
// add your code here
}
}
})

Retrieve the arguments using event.getParam('arguments'). It returns an object if there are arguments or an empty array
if there are no arguments.

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Reference aura:renderIf

Returning a Value
aura:method executes synchronously.
• A synchronous method finishes executing before it returns. Use the return statement to return a value from synchronous JavaScript
code. See Return Result for Synchronous Code.
• An asynchronous method may continue to execute after it returns. Use a callback to return a value from asynchronous JavaScript
code. See Return Result for Asynchronous Code.

SEE ALSO:
Calling Component Methods
Component Events

aura:renderIf
Deprecated. Use aura:if instead.
aura:renderIf renders the content within the tag if the isTrue attribute evaluates to true. The previous advice was to only
consider using aura:renderIf if you expect to show the components for both the true and false states, and it would require
a server round trip to instantiate the components that aren't initially rendered. This advice is no longer relevant. Always use aura:if
instead.

Attribute Name Type Description

else Component[] The markup to render when isTrue evaluates to false. Set this attribute using the
aura:set tag.

isTrue String Required. An expression that determines whether the content is displayed. If it evaluates to
true, the content is displayed.

Example
This snippet of markup uses the <aura:renderIf> tag to conditionally display an edit button.
<aura:attribute name="edit" type="Boolean" default="true">
<aura:renderIf isTrue="{!v.edit}">
<ui:button label="Edit"/>
<aura:set attribute="else">
You can’t edit this.
<!-- Imagine some components here that need to be created on the server -->
</aura:set>
</aura:renderIf>

If the edit attribute is set to true, a ui:button displays. Otherwise, the text in the else attribute displays.

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Reference aura:set

We recommend using aura:if instead if the else attribute is rarely displayed or if it doesn’t include components that need to be
created on the server.

SEE ALSO:
Best Practices for Conditional Markup
aura:if

aura:set
Use <aura:set> in markup to set the value of an attribute inherited from a super component, event, or interface.
To learn more, see:
• Setting Attributes Inherited from a Super Component
• Setting Attributes on a Component Reference
• Setting Attributes Inherited from an Interface

Setting Attributes Inherited from a Super Component

Use <aura:set> in the markup of a sub component to set the value of an inherited attribute.
Let's look at an example. Here is the c:setTagSuper component.
<!--c:setTagSuper-->
<aura:component extensible="true">
<aura:attribute name="address1" type="String" />
setTagSuper address1: {!v.address1}<br/>
</aura:component>

c:setTagSuper outputs:

setTagSuper address1:

The address1 attribute doesn't output any value yet as it hasn't been set.
Here is the c:setTagSub component that extends c:setTagSuper.
<!--c:setTagSub-->
<aura:component extends="c:setTagSuper">
<aura:set attribute="address1" value="808 State St" />
</aura:component>

c:setTagSub outputs:

setTagSuper address1: 808 State St

sampleSetTagExc:setTagSub sets a value for the address1 attribute inherited from the super component,
c:setTagSuper.

Warning: This usage of <aura:set> works for components and abstract components, but it doesn’t work for interfaces. For
more information, see Setting Attributes Inherited from an Interface on page 343.

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Reference Setting Attributes on a Component Reference

If you’re using a component by making a reference to it in your component, you can set the attribute value directly in the markup. For
example, c:setTagSuperRef makes a reference to c:setTagSuper and sets the address1 attribute directly without using
aura:set.

<!--c:setTagSuperRef-->
<aura:component>
<c:setTagSuper address1="1 Sesame St" />
</aura:component>

c:setTagSuperRef outputs:

setTagSuper address1: 1 Sesame St

SEE ALSO:
Component Body
Inherited Component Attributes
Setting Attributes on a Component Reference

Setting Attributes on a Component Reference

When you include another component, such as <ui:button>, in a component, we call that a component reference to <ui:button>.
You can use <aura:set> to set an attribute on the component reference. For example, if your component includes a reference to
<ui:button>:

<ui:button label="Save">
<aura:set attribute="buttonTitle" value="Click to save the record"/>
</ui:button>

This is equivalent to:

<ui:button label="Save" buttonTitle="Click to save the record" />

The latter syntax without aura:set makes more sense in this simple example. You can also use this simpler syntax in component
references to set values for attributes that are inherited from parent components.
aura:set is more useful when you want to set markup as the attribute value. For example, this sample specifies the markup for the
else attribute in the aura:if tag.

<aura:component>
<aura:attribute name="display" type="Boolean" default="true"/>
<aura:if isTrue="{!v.display}">
Show this if condition is true
<aura:set attribute="else">
<ui:button label="Save" press="{!c.saveRecord}" />
</aura:set>
</aura:if>
</aura:component>

SEE ALSO:
Setting Attributes Inherited from a Super Component

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Reference Setting Attributes Inherited from an Interface

Setting Attributes Inherited from an Interface

To set the value of an attribute inherited from an interface, redefine the attribute in the component and set its default value. Let’s look
at an example with the c:myIntf interface.
<!--c:myIntf-->
<aura:interface>
<aura:attribute name="myBoolean" type="Boolean" default="true" />
</aura:interface>

This component implements the interface and sets myBoolean to false.

<!--c:myIntfImpl-->
<aura:component implements="c:myIntf">
<aura:attribute name="myBoolean" type="Boolean" default="false" />

<p>myBoolean: {!v.myBoolean}</p>
</aura:component>

Messaging Component Reference

Messaging components include notifications and overlays that communicate relevant information to users. They are supported in
Lightning Experience, Salesforce app, and Lightning communities.

lightning:notificationsLibrary
lightning:notificationsLibrary provides an easy way to display messages in the app. This component requires API
version 41.0 and later. This component is supported in Lightning Experience, Salesforce app, and Lightning communities only.
Messages can be displayed in notices and toasts. Notices alert users to system-related issues and updates. Toasts enable you to provide
feedback and serve as a confirmation mechanism after the user takes an action. Include one
<lightning:notificationsLibrary aura:id="notifLib"/> tag in the component that triggers the notifications,
where aura:id is a unique local ID. Only one tag is needed for multiple notifications.

Notices
Notices interrupt the user's workflow and block everything else on the page. Notices must be acknowledged before a user regains control
over the app again. As such, use notices sparingly. They are not suitable for confirming a user’s action, such as before deleting a record.
To dismiss the notice, only the OK button is currently supported.

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Reference lightning:notificationsLibrary

Here’s an example that contains a button. When clicked, the button displays a notice with the error variant.
<aura:component>
<lightning:notificationsLibrary aura:id="notifLib"/>
<lightning:button name="notice" label="Show Notice" onclick="{!c.handleShowNotice}"/>
</aura:component>

Your client-side controller displays the notice.

({
handleShowNotice : function(component, event, helper) {
component.find('notifLib').showNotice({
"variant": "error",
"header": "Something has gone wrong!",
"message": "Unfortunately, there was a problem updating the record.",
closeCallback: function() {
alert('You closed the alert!');
}
});
}
})

To create and display a notice, pass in the notice attributes using component.find('notifLib').showNotice(), where
notifLib matches the aura:id on the lightning:notificationsLibrary instance.
Notices inherit styling from prompts in the Lightning Design System.
Attributes

Attribute Name Attribute Type Description Required?

header String The heading that’s displayed at the top of the notice.

title String The title of the notice, displayed in bold.

message String The message within the notice body. New lines are replaced by <br/>
and text links by anchors.

variant String Changes the appearance of the notice. Accepted variants are info,
warning, and error. This value defaults to info.

closeCallback Function A callback that’s called when the notice is closed.

Toasts
Toasts are less intrusive than notices and are suitable for providing feedback to a user following an action, such as after a record is created.
A toast can be dismissed or can remain visible until a predefined duration has elapsed.

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Reference lightning:overlayLibrary

Here’s an example that contains a button. When clicked, the button displays a toast with the info variant and remains visible until
you press the close button, denoted by the X in the top right corner.
<aura:component>
<lightning:notificationsLibrary aura:id="notifLib"/>
<lightning:button name="toast" label="Show Toast" onclick="{!c.handleShowToast}"/>
</aura:component>

Your client-side controller displays the toast.

({
handleShowToast : function(component, event, helper) {
component.find('notifLib').showToast({
"title": "Notif library Success!",
"message": "The record has been updated successfully."
});
}
})

To create and display a toast, pass in the toast attributes using component.find('notifLib').showToast(), where
notifLib matches the aura:id on the lightning:notificationsLibrary instance.
Toasts inherit styling from toasts in the Lightning Design System.
Attributes

Attribute Name Attribute Type Description Required?

title String The title of the toast, displayed as a heading.

message String A string representing the message. It can contain placeholders in the
form of {0} ... {N}. This placeholders will be replaced with the action
links on the message data.

messageData Object Array of inlined action links to replace within the toast message template.

variant String Changes the appearance of the toast. Accepted variants are info,
success, warning, and error. This value defaults to info.

mode String Determines how persistent the toast is. The default is dismissable.
Valid modes are:
• dismissable: Remains visible until you press the close button
or 3 seconds has elapsed, whichever comes first.
• pester: Remains visible until the close button is clicked.
• sticky: Remains visible for 3 seconds.

lightning:overlayLibrary
lightning:overlayLibrary provides an easy way to display relevant information and feedback. This component requires API
version 41.0 and later. This component is supported in Lightning Experience, Salesforce app, and Lightning communities only.
Messages can be displayed in modals and popovers. Modals display a dialog in the foreground of the app, interrupting a user’s workflow
and drawing attention to the message. Popovers display relevant information when you hover over a reference element. Include one

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Reference lightning:overlayLibrary

<lightning:overlayLibrary aura:id="overlayLib"/> tag in the component that triggers the messages, where
aura:id is a unique local ID. Only one tag is needed for multiple messages.

Modals
A modal blocks everything else on the page until it’s dismissed. A modal must be acknowledged before a user regains control over the
app again. A modal is triggered by user interaction, which can be a click of a button or link. The modal header, body, and footer are
customizable. Pressing the Escape key or clicking the close button closes the modal.

Here’s an example that contains a button. When clicked, the button displays a modal with a custom body.
<aura:component>
<lightning:overlayLibrary aura:id="overlayLib"/>
<lightning:button name="modal" label="Show Modal" onclick="{!c.handleShowModal}"/>
</aura:component>

Your client-side controller displays the modal. To create and display a modal, pass in the modal attributes using
component.find('overlayLib').showCustomModal(), where overlayLib matches the aura:id on the
lightning:overlayLibrary instance.

({
handleShowModal: function(component, evt, helper) {
var modalBody;
$A.createComponent("c:modalContent", {},
function(content, status) {
if (status === "SUCCESS") {
modalBody = content;
component.find('overlayLib').showCustomModal({
header: "Application Confirmation",
body: modalBody,
showCloseButton: true,
cssClass: "mymodal",
closeCallback: function() {
alert('You closed the alert!');
}
})

});
}
})

346
Reference lightning:overlayLibrary

c:modalContent is a custom component that displays an icon and message.

<aura:component>
<lightning:icon size="medium" iconName="action:approval" alternativeText="Approved"
/>
Your application has been approved.
</aura:component>

You can pass in your own footer via the footer attribute. This example creates a custom body and footer using
$A.createComponents().

handleShowModalFooter : function (component, event, helper) {

var modalBody;
var modalFooter;
$A.createComponents([
["c:modalContent",{}],
["c:modalFooter",{}]
],
function(components, status){
if (status === "SUCCESS") {
modalBody = components[0];
modalFooter = components[1];
component.find('overlayLib').showCustomModal({
header: "Application Confirmation",
body: modalBody,
footer: modalFooter,
showCloseButton: true,
cssClass: "my-modal,my-custom-class,my-other-class",
closeCallback: function() {
alert('You closed the alert!');
}
})
}
}
);
}

c:modalFooter is a custom component that displays two buttons.

<aura:component>
<lightning:overlayLibrary aura:id="overlayLib"/>
<lightning:button name="cancel" label="Cancel" onclick="{!c.handleCancel}"/>
<lightning:button name="ok" label="OK" variant="brand" onclick="{!c.handleOK}"/>
</aura:component>

Define what happens when you click the buttons in your client-side controller.
({
handleCancel : function(component, event, helper) {
//closes the modal or popover from the component
component.find("overlayLib").notifyClose();
},
handleOK : function(component, event, helper) {
//do something
}
})

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Reference lightning:overlayLibrary

showCustomModal() and showCustomPopover() return a promise, which is useful if you want to get a reference to the
modal when it’s displayed.
component.find('overlayLib').showCustomModal({
//modal attributes
}).then(function (overlay) {
//closes the modal immediately
overlay.close();
});

Modals inherit styling from modals in the Lightning Design System.

Attributes

Attribute Name Attribute Type Description Required?

header Object The heading that’s displayed at the top of the modal.

body Object The body of the modal.

footer Object The modal footer.

showCloseButton Boolean Specifies whether to display the close button on the modal. The default
is true.

cssClass String A comma-separated list of CSS classes for the modal. Applies to visible
markup only.

closeCallback Function A callback that’s called when the modal is closed.

Methods
You can use the following methods on the modal instance returned by the promise.
close(): Dismisses and destroys the modal.
hide(): Hides the modal from view.
show(): Displays the modal.

Popovers
Popovers display contextual information on a reference element and don’t interrupt like modals. A popover can be displayed when you
hover over or click the reference element. Pressing the Escape key closes the popover. The default positioning of the popover is on the
right of the reference element.

Here’s an example that contains a button and a reference div element. When clicked, the button displays a popover. The popover also
displays when you hover over the div element.
<aura:component>
<lightning:overlayLibrary aura:id="overlayLib"/>
<lightning:button name="popover" label="Show Popover" onclick="{!c.handleShowPopover}"/>

348
Reference lightning:overlayLibrary

<div class="mypopover" onmouseover="{!c.handleShowPopover}">Popover should display if

you hover over here.</div>
</aura:component>

Your client-side controller displays the popover. Although this example passes in a string to the popover body, you can also pass in a
custom component like in the previous modal example. Any custom CSS class you add must be accompanied by the cMyCmp class,
where c is your namespace and MyCmp is the name of the component that creates the popover. Adding this class ensures that the
custom styling is properly scoped.
({
handleShowPopover : function(component, event, helper) {
component.find('overlayLib').showCustomPopover({
body: "Popovers are positioned relative to a reference element",
referenceSelector: ".mypopover",
cssClass: "popoverclass, cMyCmp"
}).then(function (overlay) {
setTimeout(function(){
//close the popover after 3 seconds
overlay.close();
}, 3000);
});
}
})

To create and display a popover, pass in the popover attributes using

component.find('overlayLib').showCustomPopover(), where overlayLib matches the aura:id on the
lightning:overlayLibrary instance.
The CSS class sets the minimum height on the popover.
.THIS.popoverclass {
min-height: 100px;
}

Popovers inherit styling from popovers in the Lightning Design System.

To append popover modifier classes, include them in cssClass. The following example adds the slds-popover_walkthrough
class for a dark theme. The pointer is hidden and replaced by the slds-nubbin_left class. To hide the pointer, add the following
CSS rule.
.THIS.no-pointer .pointer{
visibility: hidden;
}

Update the cssClass attribute. The cMyCmp class corresponds to your namespace and component name, and is case-sensitive.
cssClass: "slds-nubbin_left,slds-popover_walkthrough,no-pointer,cMyCmp"

Attributes

Attribute Name Attribute Type Description Required?

body Object The body of the popover.

referenceSelector Object The reference element to which the popover is appended. The popover
is appended to the right of the reference element.

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Reference System Event Reference

Attribute Name Attribute Type Description Required?

cssClass String A comma-separated list of CSS classes for the popover. Applies to visible
markup only.

Methods
You can use the following methods on the modal instance returned by the promise.
close(): Dismisses and destroys the modal.
hide(): Hides the modal from view.
show(): Displays the modal.

System Event Reference

System events are fired by the framework during its lifecycle. You can handle these events in your Lightning apps or components, and
within the Salesforce mobile app. For example, these events enable you to handle attribute value changes, URL changes, or when the
app or component is waiting for a server response.

aura:doneRendering
Indicates that the initial rendering of the root application has completed.

Note: We don't recommend using the legacy aura:doneRendering event except as a last resort. Unless your component
is running in complete isolation in a standalone app and not included in complex apps, such as Lightning Experience or the
Salesforce app, you probably don’t want to handle this application event. The container app may trigger your event handler
multiple times.
This event is automatically fired if no more components need to be rendered or rerendered due to any attribute value changes. The
aura:doneRendering event is handled by a client-side controller. A component can have only one <aura:handler> tag
to handle this event.
<aura:handler event="aura:doneRendering" action="{!c.doneRendering}"/>

For example, you want to customize the behavior of your app after it’s finished rendering the first time but not after subsequent
rerenderings. Create an attribute to determine if it’s the first rendering.
<aura:component>
<aura:handler event="aura:doneRendering" action="{!c.doneRendering}"/>
<aura:attribute name="isDoneRendering" type="Boolean" default="false"/>
<!-- Other component markup here -->
<p>My component</p>
</aura:component>

This client-side controller checks that the aura:doneRendering event has been fired only once.
({
doneRendering: function(cmp, event, helper) {
if(!cmp.get("v.isDoneRendering")){
cmp.set("v.isDoneRendering", true);
//do something after component is first rendered
}

350
Reference aura:doneWaiting

}
})

Note: When aura:doneRendering is fired, component.isRendered() returns true. To check if your element is
visible in the DOM, use utilities such as component.getElement(), component.hasClass(), or
element.style.display.
The aura:doneRendering handler contains these required attributes.

Attribute Name Type Description

event String The name of the event, which must be set to aura:doneRendering.

action Object The client-side controller action that handles the event.

aura:doneWaiting
Indicates that the app is done waiting for a response to a server request. This event is preceded by an aura:waiting event. This
event is fired after aura:waiting.

Note: We don't recommend using the legacy aura:doneWaiting event except as a last resort. The aura:doneWaiting
application event is fired for every server response, even for responses from other components in your app. Unless your component
is running in complete isolation in a standalone app and not included in Lightning Experience or the Salesforce app, you probably
don’t want to handle this application event. The container app may fire server-side actions and trigger your event handler multiple
times.
This event is automatically fired if no more response from the server is expected. The aura:doneWaiting event is handled by a
client-side controller. A component can have only one <aura:handler> tag to handle this event.
<aura:handler event="aura:doneWaiting" action="{!c.hideSpinner}"/>

This example hides a spinner when aura:doneWaiting is fired.

<aura:component>
<aura:handler event="aura:doneWaiting" action="{!c.hideSpinner}"/>
<!-- Other component markup here -->
<center><ui:spinner aura:id="spinner"/></center>
</aura:component>

This client-side controller fires an event that hides the spinner.

({
hideSpinner : function (component, event, helper) {
var spinner = component.find('spinner');
var evt = spinner.get("e.toggle");
evt.setParams({ isVisible : false });
evt.fire();
}
})

The aura:doneWaiting handler contains these required attributes.

Attribute Name Type Description

event String The name of the event, which must be set to aura:doneWaiting.

351
Reference aura:locationChange

Attribute Name Type Description

action Object The client-side controller action that handles the event.

aura:locationChange
Indicates that the hash part of the URL has changed.
This event is automatically fired when the hash part of the URL has changed, such as when a new location token is appended to the
hash. The aura:locationChange event is handled by a client-side controller. A component can have only one <aura:handler
event="aura:locationChange"> tag to handle this event.

<aura:handler event="aura:locationChange" action="{!c.update}"/>

This client-side controller handles the aura:locationChange event.

({
update : function (component, event, helper) {
// Get the new location token from the event
var loc = event.getParam("token");
// Do something else
}
})

The aura:locationChange handler contains these required attributes.

Attribute Name Type Description

event String The name of the event, which must be set to aura:locationChange.

action Object The client-side controller action that handles the event.

The aura:locationChange event contains these attributes.

Attribute Name Type Description

token String The hash part of the URL.

querystring Object The query string portion of the hash.

aura:systemError
Indicates that an error has occurred.
This event is fired when a $A.auraFriendlyError error is thrown. Handle the aura:systemError event in a client-side
controller. A component can have only one <aura:handler event="aura:systemError"> tag in markup to handle this
event.
<aura:handler event="aura:systemError" action="{!c.handleError}"/>

Throw the error using $A.auraFriendlyError("error message here").

352
Reference aura:valueChange

Set the error message in the message property of AuraFriendlyError, which corresponds to the first argument of
$A.auraFriendlyError(). Set an optional object with more context in the data property of AuraFriendlyError.

({
throwError : function(cmp, event){
// error is an instance of AuraFriendlyError
// argument sets the message property of AuraFriendlyError
var error = new $A.auraFriendlyError("This is a sample error.");
// set an optional error data object
error.data = {
"moreErrorData1": "more1",
"moreErrorData2": "more2",
};
throw error;
},
})

Set event["handled"]=true in the client-side controller action that handles the aura:systemError event to indicate
that you’re providing your own error handler.
The aura:handler tag for the aura:systemError event contains these required attributes.

Attribute Name Type Description

event String The name of the event, which must be set to aura:systemError.

action Object The client-side controller action that handles the event.

The aura:systemError event contains these attributes. You can retrieve the attribute values using
event.getParam("attributeName").

Attribute Name Type Description

message String The error message.

error String The name of the error, AuraFriendlyError.

auraError Object The AuraFriendlyError error object.

SEE ALSO:
Throwing and Handling Errors

aura:valueChange
Indicates that an attribute value has changed.
This event is automatically fired when an attribute value changes. The aura:valueChange event is handled by a client-side
controller. A component can have multiple <aura:handler name="change"> tags to detect changes to different attributes.
<aura:handler name="change" value="{!v.items}" action="{!c.itemsChange}"/>

353
Reference aura:valueDestroy

This example updates a Boolean value, which automatically fires the aura:valueChange event.
<aura:component>
<aura:attribute name="myBool" type="Boolean" default="true"/>

<!-- Handles the aura:valueChange event -->

<aura:handler name="change" value="{!v.myBool}" action="{!c.handleValueChange}"/>
<ui:button label="change value" press="{!c.changeValue}"/>
</aura:component>

These client-side controller actions trigger the value change and handle it.
({
changeValue : function (component, event, helper) {
component.set("v.myBool", false);
},

handleValueChange : function (component, event, helper) {

// handle value change
console.log("old value: " + event.getParam("oldValue"));
console.log("current value: " + event.getParam("value"));
}
})

The valueChange event gives you access to the previous value (oldValue) and the current value (value) in the handler action.
In this example, oldValue returns true and value returns false.
The change handler contains these required attributes.

Attribute Name Type Description

name String The name of the handler, which must be set to change.

value Object The attribute for which you want to detect changes.

action Object The client-side controller action that handles the value change.

SEE ALSO:
Detecting Data Changes with Change Handlers

aura:valueDestroy
Indicates that a component has been destroyed. Handle this event if you need to do custom cleanup when a component is destroyed.
This event is automatically fired when a component is being destroyed. The aura:valueDestroy event is handled by a client-side
controller.
A component can have only one <aura:handler name="destroy"> tag to handle this event.
<aura:handler name="destroy" value="{!this}" action="{!c.handleDestroy}"/>

This client-side controller handles the aura:valueDestroy event.

({
handleDestroy : function (component, event, helper) {
var val = event.getParam("value");

354
Reference aura:valueInit

// Do something else here

}
})

Let’s say that you are viewing a component in the Salesforce app. The aura:valueDestroy event is triggered when you tap on
a different menu item on the Salesforce mobile navigation menu, and your component is destroyed. In this example, the value
parameter in the event returns the component that’s being destroyed.
The <aura:handler> tag for the aura:valueDestroy event contains these required attributes.

Attribute Name Type Description

name String The name of the handler, which must be set to destroy.

value Object The value for which you want to detect the event for. The value that is being destroyed.
Always set value="{!this}".

action Object The client-side controller action that handles the destroy event.

The aura:valueDestroy event contains these attributes.

Attribute Name Type Description

value String The component being destroyed, which is retrieved via
event.getParam("value").

aura:valueInit
Indicates that an app or component has been initialized.
This event is automatically fired when an app or component is initialized, prior to rendering. The aura:valueInit event is handled
by a client-side controller. A component can have only one <aura:handler name="init"> tag to handle this event.
<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

For an example, see Invoking Actions on Component Initialization on page 151.

Note: Setting value="{!this}" marks this as a value event. You should always use this setting for an init event.

The init handler contains these required attributes.

Attribute Name Type Description

name String The name of the handler, which must be set to init.

value Object The value that is initialized, which must be set to {!this}.

action Object The client-side controller action that handles the value change.

SEE ALSO:
Invoking Actions on Component Initialization
aura:valueRender

355
Reference aura:valueRender

aura:valueRender
Indicates that an app or component has been rendered or rerendered.
This event is automatically fired when an app or component is rendered or rerendered. The aura:valueRender event is handled
by a client-side controller. A component can have only one <aura:handler name="render"> tag to handle this event.
<aura:handler name="render" value="{!this}" action="{!c.onRender}"/>

In this example, the onRender action in your client-side controller handles initial rendering and rerendering of the component. You
can choose any name for the action attribute.

Note: Setting value="{!this}" marks this as a value event. You should always use this setting for a render event.

The render event is fired after the init event, which is fired after component construction but before rendering.
The aura:valueRender event contains one attribute.

Attribute Name Attribute Type Description

value Object The component that rendered or rerendered.

SEE ALSO:
aura:valueInit
Events Fired During the Rendering Lifecycle

aura:waiting
Indicates that the app is waiting for a response to a server request. This event is fired before aura:doneWaiting.

Note: We don't recommend using the legacy aura:waiting event except as a last resort. The aura:waiting application
event is fired for every server request, even for requests from other components in your app. Unless your component is running
in complete isolation in a standalone app and not included in Lightning Experience or the Salesforce app, you probably don’t want
to handle this application event. The container app may fire server-side actions and trigger your event handler multiple times.
This event is automatically fired when a server-side action is added using $A.enqueueAction() and subsequently run, or when
it’s expecting a response from an Apex controller. The aura:waiting event is handled by a client-side controller. A component can
have only one <aura:handler> tag to handle this event.
<aura:handler event="aura:waiting" action="{!c.showSpinner}"/>

This example shows a spinner when aura:waiting is fired.

<aura:component>
<aura:handler event="aura:waiting" action="{!c.showSpinner}"/>
<!-- Other component markup here -->
<center><ui:spinner aura:id="spinner"/></center>
</aura:component>

This client-side controller fires an event that displays the spinner.

({
showSpinner : function (component, event, helper) {
var spinner = component.find('spinner');

356
Reference Supported HTML Tags

var evt = spinner.get("e.toggle");

evt.setParams({ isVisible : true });
evt.fire();
}
})

The aura:waiting handler contains these required attributes.

Attribute Name Type Description

event String The name of the event, which must be set to aura:waiting.

action Object The client-side controller action that handles the event.

Supported HTML Tags

The framework supports most HTML tags, including the majority of HTML5 tags.
An HTML tag is treated as a first-class component by the framework. Each HTML tag is translated into an <aura:html> component,
allowing it to enjoy the same rights and privileges as any other component.
For example, the framework automatically converts a standard HTML <div> tag to this component:
<aura:html tag="div" />

We recommend that you use components in preference to HTML tags. For example, use ui:button instead of <button>.
Components are designed with accessibility in mind so users with disabilities or those who use assistive technologies can also use your
app. When you start building more complex components, the reusable out-of-the-box components can simplify your job by handling
some of the plumbing that you would otherwise have to create yourself. Also, these components are secure and optimized for performance.
Note that you must use strict XHTML. For example, use <br/> instead of <br>.
Some HTML tags are unsafe or unnecessary. The framework doesn’t support these tags.
The HtmlTag enum in this open-source Aura file lists the supported HTML tags. Any tag followed by (false) is not supported.
For example, applet(false) means the applet tag isn't supported.

SEE ALSO:
Supporting Accessibility

Anchor Tag: <a>

Don’t hard code or dynamically generate Salesforce URLs in the href attribute of an <a> tag. Use events, such as
force:navigateToSObject or force:navigateToURL, instead.

Avoid the href Attribute

Using the href attribute of an <a> tag leads to inconsistent behavior in different apps and shouldn’t be relied on. For example, don’t
use this markup to link to a record:
<a href="/XXXXXXXXXXXXXXXXXX">Salesforce record ID (DON'T DO THIS)</a>

357
Reference Anchor Tag: <a>

If you use # in the href attribute, a secondary issue occurs. The hash mark (#) is a URL fragment identifier and is often used in Web
development for navigation within a page. Avoid # in the href attribute of anchor tags in Lightning components as it can cause
unexpected navigation changes, especially in the Salesforce app. That’s another reason not to use href.

Use Navigation Events

Use one of the navigation events for consistent behavior across Lightning Experience, Salesforce app, and Lightning communities.
force:navigateToList
Navigates to a list view.
force:navigateToObjectHome
Navigates to an object home.
force:navigateToRelatedList
Navigates to a related list.
force:navigateToSObject
Navigates to a record.
force:navigateToURL
Navigates to a URL.
As well as consistent behavior, using navigation events instead of <a> tags reduces the number of full app reloads, leading to better
performance.

Example Using Navigation Event

This example uses an <a> tag that’s wired to a controller action, which fires the force:navigateToSObject event to navigate
to a record. The one.app container handles the event. This event is supported in Lightning Experience, Salesforce app, and Lightning
communities.
<!--c:navToRecord-->
<aura:component>
<aura:attribute name="recordId" type="String" />

<p><a onclick="{!c.handleClick}">link to record</a></p>

</aura:component>

Here is the controller that fires the event.

/* navToRecordController.js */
({
handleClick: function (component, event, helper) {
var navEvt = $A.get("e.force:navigateToSObject");
navEvt.setParams({
"recordId": component.get("v.recordId")
});
navEvt.fire();
}
})

The record ID is passed into c:navToRecord by setting its recordId attribute. When c:navToRecord is used in Lightning
Experience, Salesforce app, or Lightning communities, the link navigates to the specified record.

358
APPENDIX

CHAPTER 15 Aura Request Lifecycle

In this chapter ... This section shows how Aura handles the initial request for an application, as well as a component
request. You can use Aura without knowing these details but read on if you are curious about how things
• Initial Application work under the covers.
Request
• Component Request
Lifecycle

359
Aura Request Lifecycle Initial Application Request

Initial Application Request

When you make a request to load an application on a browser, Aura returns an HTTP response with a default template, denoted by the
template attribute in the .app file. The template contains JavaScript tags that make requests to get your application data.
The browser renders the specified template and loads the Aura engine and the component definitions in the dependency tree of the
app. The Aura engine renders the requested application. The Aura engine processes the application markup, and translates the component
markup to HTML objects, returning the DOM elements that are rendered to the browser.
This diagram illustrates the component request lifecycle.

SEE ALSO:
Component Request Overview

360
Aura Request Lifecycle Component Request Lifecycle

Component Request Lifecycle

When a component is requested, Aura retrieves the relevant metadata and data from the server to construct the component. The
framework uses the metadata and data to construct the component on the client, enabling the client to render the component.

IN THIS SECTION:
Component Request Overview
Server-Side Processing for Component Requests
Client-Side Processing for Component Requests
Component Request Glossary

Component Request Overview

Aura performs initial construction of a component on the server. The client completes the initialization process and manages any
rendering or rerendering.
Before we explore the component request process, it’s important to understand these terms.

Term Description
Definition Each definition describes metadata for an element, such as a component, event, controller, or model. A
large part of Aura is a registry of definitions for its various elements.
A definition's metadata can include a name, location of origin, and descriptor (DefDescriptor, the primary
key of the definition).

DefDescriptor A DefDescriptor acts as a key for a definition in a registry. It's an Aura class that contains the metadata for
any definition used in Aura, such as a component, action, or event. In the example of a model, it is a nicely
parsed description of model="java://myPackage.MyClass" with methods to retrieve the
language, class name, and package name. Rather than passing a more heavyweight definition around in
code, Aura usually passes around a DefDescriptor instead.
The qualified name for a DefDescriptor has a format of either prefix://namespace:name or
prefix://namespace.name. For example, js://ui.button.
• prefix: Defines the language, such as JavaScript or Java
• namespace: Corresponds to the package name or XML namespace
• name: Corresponds to the class name or local name

Instance An instance represents the data for a component, event, or action. The component data is contained in its
model and attributes.

Registry Registries store metadata definitions. Some registries last for the duration of a request, while others are
cached for the lifetime of the app server. They may be created during the request process and destroyed
when the server completes the request. A master definition registry contains a list of registries for each Aura
resource.

Let's see what happens when a client requests a component at the server via an HTTP request in the form
http://<yourServer>/namespace/<component>.cmp.

361
Aura Request Lifecycle Server-Side Processing for Component Requests

Here's how a component request is processed on the server and client:

The server:
1. Loads registries and locates component definitions
2. Builds or retrieves component definitions
3. Instantiates component definitions
4. Serializes component definitions and instances
5. Sends serialized component definitions and instances to the client
The client:
1. Deserializes the response to create a metadata tree
2. Traverses the metadata tree to create an instance tree
3. Traverses the instance tree to render the component
4. Renders the component

SEE ALSO:
Server-Side Processing for Component Requests
Client-Side Processing for Component Requests

Server-Side Processing for Component Requests

A component lifecycle starts when the client sends an HTTP request to the server, which can be in the form
http://<yourServer>/<namespace>/<component>.cmp. Attributes can be included in the query string, such as
http://<yourServer>/<namespace>/<component>.cmp?title=Component1. If attributes are not specified, the
defaults that are defined in the attribute definition are used.
For a component request, the server:
1. Load registries and locates component definitions.
2. Build or retrieves component definitions.
3. Instantiate component definitions.
4. Serialize component definitions and instances.
5. Send serialized component definitions and instances to the client.

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Aura Request Lifecycle Server-Side Processing for Component Requests

1. Load registries and locate component definitions.

When the server receives an HTTP request, the Aura framework is loaded according to the specified mode. AuraContextFilter
creates a AuraContext, which contains the mode denoted by the aura.mode parameter in the URL, such as in
http://<yourServer>/namespace/<component>.cmp?aura.mode=PROD. Aura uses the default mode if the
aura.mode parameter is not included in the query string.
The server receives and parses the request for an instance of a component definition (ComponentDef). If attributes are included, Aura
converts them to strongly typed attributes for the component definition.
Next, the registries are loaded. Registries store metadata for Aura objects. They may be created during the request process and destroyed
when the server completes the request.
A master definition registry (MasterDefRegistry) contains a list of registries (DefRegistry) that are used to load and cache
definitions. A separate registry is used for each Aura object, such as actions, or controllers.

2. Build or retrieve component definitions.

This stage of the process retrieves the component's metadata, known as the ComponentDef.
After the relevant registries are identified, the server determines if the requested ComponentDef is already cached.
• If it's cached in a registry or found in other locations, the ComponentDef is returned and the component definition tree is updated
to include the definition. The ComponentDef is cached, including its references to other ComponentDefs, attributes, events,
controller, and resources, such as CSS styles.
• If the ComponentDef is not cached, the server locates and parses the source code to construct the ComponentDef. The server
also identifies the language and definition type of the ComponentDef.
Any dependencies on other definitions are also determined. Dependencies may include definitions for interfaces, controllers, actions,
and models. A DefRegistry that doesn't contain the ComponentDef passes the request to a DefFactory, which builds the
definition.
Each component definition in the tree is parsed iteratively. The process is completed when the ComponentDef tree doesn't contain
any unparsed ComponentDefs.

3. Instantiate component definitions.

Once the server completes the component definition process, it can create a component instance. To start this instantiation, the
ComponentDef (a root definition) is retrieved along with any attribute definitions and references to other components. The next
steps are:
• Determine component definition type: Aura determines whether the root component definition is abstract or concrete.
• Create component instances:
– Abstract: Aura can instantiate abstract component definitions using a provider to determine the concrete component to use
at runtime.
– Concrete: Aura constructs a component instance and any properties associated with it, along with its super component. Attribute
values of the component definitions are loaded, and can consist of other component definitions, which are instantiated recursively.

• Create model instances: After the super component definition is instantiated, Aura creates any associated component model that
hasn't been instantiated.
• Create attribute instances: Aura instantiates all remaining attributes. If the attribute refers to an uninstantiated component
definition, the latter is instantiated. Non-component attribute values may come from a client request as a literal or expression, which
can be derived from a super component definition, a model, or other component definitions. Expressions can be resolved on the
client side to allow data to be refreshed dynamically.

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Aura Request Lifecycle Client-Side Processing for Component Requests

The instantiation process terminates when the component and all its child nodes have been instantiated. Note that controllers are not
instantiated since they are static and don't have any state.

4. Serialize component definition and instances.

Aura enables dynamic rendering on the client side through a JSON serialization process, which begins after instantiation completes.
Aura serializes:
• The component instance tree
• Data for the component instance tree
• Metadata for the component instance tree
When the current object has been serialized but it's not the root object corresponding to the requested component, its parent objects
are serialized recursively.

5. Send serialized component definitions and instances to client.

The server sends the serialized component definitions and instances to the client. Definitions are cached but the instance data is not
cached.
The definitions are transmitted in the following format:
{"descriptor":"markup://aura:component",
"rendererDef":{ "serRefId":2},
"attributeDefs":[{ "serId":20,
"value":{ "descriptor":"body",
"typeDefDescriptor":"aura://Aura.Component[]",
"required":false} } ],
"interfaces":["markup://aura:rootComponent"],
"isAbstract":true}

The component instance tree is transmitted in the following format:

$A.initAsync({"context":{"mode":"DEV","app":"auradocs:sample",
"requestedLocales":["en_US","en"]},
"deftype":"APPLICATION",
"descriptor":"markup://auradocs:sample",
"host":"",
"lastmod":1323498293847});

SEE ALSO:
Server-Side Runtime Binding of Components
Initial Application Request
Component Request Glossary

Client-Side Processing for Component Requests

After the server processes the request, it returns the component definitions (metadata for the all required components) and instance
tree (data) in JSON format.
The client performs these tasks:
1. Deserialize the response to create a metadata tree.

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Aura Request Lifecycle Component Request Glossary

2. Traverse the metadata tree to create an instance tree.

3. Traverse the instance tree to render the component.
4. Render the components.

1. Deserialize the response to create a metadata tree.

The JSON representation of the component definition is deserialized to create a metadata structure (JavaScript objects or maps). By
default, any Map, Array, Number, Boolean, String or nulls are supported for serialization and deserialization. Other objects can provide
custom serialization by implementing the JsonSerializable interface.

2. Traverse the metadata tree to create an instance tree.

The client traverses the JavaScript tree to initialize objects from the deserialized tree. The tree can contain:
• Definition: The client initializes the definition.
• Descriptor only: The client knows that definition has been pre-loaded and cached.
As part of component initialization, client-side framework code are cached alongside your JavaScript code and CSS.

3. Traverse the instance tree to render the component.

After component initialization, the client traverses the instance tree to render the component instance. The reference IDs are used to
recreate the component references, which can point to a ComponentDef, a model, or a controller.

4. Render the components.

The client locates the renderer definition in the component bundle, or uses the default renderer method to render the component and
any sub-components recursively. This adds the components to the DOM. For more information on the rendering lifecycle, see Events
Fired During the Rendering Lifecycle on page 127.

SEE ALSO:
Server-Side Rendering to the DOM
Initial Application Request
Component Request Glossary

Component Request Glossary

This glossary explains terms related to Aura definitions and registries.

Definition-related Example Description

Term
Definition aura:component Each definition describes metadata for an object, such as a
component, event, controller, or model. A large part of Aura is a
registry of definitions for its various objects.

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Aura Request Lifecycle Component Request Glossary

Definition-related Example Description

Term
A definition's metadata can include a name, location of origin,
and descriptor (DefDescriptor, the primary key of the
definition).
A component definition can be used by other component
definitions and can extend another component definition.

Root Definition ComponentDef Top-level definition. Markup language for a root definition can
InterfaceDef include a pointer to another definition, and references to the
descriptors of associate definitions.
EventDef

Associate Definition ControllerDef Associate definitions represent objects that are associated with a
ModelDef root definition. An instance of an associate definition can be shared
by multiple root definitions. Associate definitions have their own
ProviderDef factories, parsers, and caching layers.
RendererDef
StyleDef
TestSuiteDef

Subdefinition AttributeDef Subdefinitions can be used to define root definitions or associate

RegisterEventDef definitions. They are stored directly on their parent definitions.

ActionDef
For example, a ComponentDef can include multiple
AttributeDef objects, and a ControllerDef can
TestCaseDef include multiple ActionDef objects.
ValueDef

Definition Reference DefRef A subdefinition that points to another definition. At runtime, it

ComponentDefRef can be turned into an instance of the definition to which it points.

AttributeDefRef
For example, when a component is instantiated, the component
definition can include attribute definition references for each
component attribute. The attribute definition reference points to
the underlying attribute definition.

Provider For abstract definition types. A provider determines the concrete

ComponentDef to instantiate for each abstract
ComponentDef. A provider enables an abstract component
definition to be used directly in markup.

Registry-related Terms Example Description

Master Definition Registry MasterDefRegistry MasterDefRegistry is a top-level
DefRegistry that lives for the duration
of a request. It is a thin redirector to various

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Aura Request Lifecycle Component Request Glossary

Registry-related Terms Example Description

long-lived definition registries that load and
cache definitions.

Definition Registry DefRegistry A DefRegistry loads and caches a list

of definitions, such as ActionDef,
ApplicationDef, ComponentDef,
or ControllerDef. A separate registry
is used for all Aura objects. If the definition
is not found, the request is passed to
DefFactory, an interface that builds the
definition.

Definition Descriptor DefDescriptor A DefDescriptor acts as a key for a

definition in a registry. It's a class that
contains the metadata for any definition
used in Aura, such as a component, action,
or event. In the example of a model, it is a
nicely parsed description of
model="java://myPackage.MyClass"
with methods to retrieve the language, class
name, and package name. Rather than
passing a more heavyweight definition
around in code, Aura usually passes around
a DefDescriptor instead.
The qualified name for a
DefDescriptor has the format
prefix://namespace:name.
• prefix: Defines the language, such as
JavaScript or Java
• namespace: Corresponds to the
package name or XML namespace
• name: Corresponds to the class name
or local name

367
INDEX

$Browser 32–33 Application (continued)

$Label 32, 45 initial request 360
$Locale 32, 34 layout and UI 132
styling 140
A styling with flavors 142, 144
Access control Application cache
application 237 browser support 249
attribute 238 overview 249
component 238 Application events
event 238 bubble 112
interface 237 capture 112
JavaScript 169 create 113
accessibility fire 114
error codes 91 handling 115
Accessibility phases 112
audio messages 88 propagation 112
buttons 87 Application templates
carousels 87 external CSS 133
dialog 90 JavaScript libraries 133
events 90 Applications
help and error messages 88 CSS 141, 144
images 89 overview 132
images, informational and decorative 89 styling 141, 144
menus 91 token 144
Action states Apps
calling server-side 205 overview 132
Actions Attribute types
background 206 Aura.Action 328
caboose 211 Aura.Component 328
calling server-side 203 basic 324
queueing 206 collection 325
storable 208–210 custom Java class 327
Adapters Function 325
overriding 312 Object 325
anchor tag 357 Attribute value, setting 341
Anti-patterns Attributes
events 127 component reference, setting on 342
API calls 182 interface, setting on 343
Application JavaScript 157
attributes 329 super component, setting on 341
aura:application 329 Aura
building and running 5 request lifecycle 359
creating 131 Aura source
creating, from command line 6 building 8
creating, in Eclipse 6 aura:application 329
flavors in namespace, applying 144 aura:attribute 323

368
Index

aura:clientLibrary 333 Component (continued)

aura:component 331 body, setting and accessing 21
aura:dependency 334 definition 365
aura:doneRendering 350 documentation 51
aura:doneWaiting 351 iteration 337
aura:event 335 metadata 365
aura:if 23, 27, 336 namespace and directory 7
aura:interface 337 nest 19
aura:iteration 337 registry 365
aura:locationChange 352 rendering 356
aura:method rendering conditionally 336, 340
result asynchronous code 178 rendering lifecycle 127
result synchronous code 176 request lifecycle 361
aura:renderIf 340 request overview 361
aura:set 341–342 themes, vendor prefixes 142
aura:systemError 352 Component attributes
aura:template 133 inheritance 241
aura:valueChange 353 Component body
aura:valueDestroy 354 JavaScript 158
aura:valueInit 355 Component bundles 11, 14
aura:valueRender 356 Component definitions
aura:waiting 356 dependency 334
Aura.Action 328 Component events
AuraLocalizationService 193 bubble 101
capture 101
B create 102
Beacons 306 fire 102
Benefits 2 handling 103–104
Best practices handling dynamically 109
events 126 phases 101
Body propagation 101
JavaScript 158 Component facets 22
Bubbling 105, 116 Component initialization 355
Buttons Component request
lightning:button 192 client-side processing 364
local ID 192 Server-side processing 362
pressed 192 ComponentDefRef 217
ui:button 192 Components
access control 169
C calling methods 174, 176, 178
Capture 105, 116 conditional markup 23
Change handlers 186, 353 creating 184
Client-side controllers 98 creating server-side 216
Component CSS 141, 144
abstract 243 flow variables, get 82
adding to an app 7 flow, finish behavior 83
attributes 17 flow, output variables 82
aura:component 331 flow, resume 84
aura:interface 337 HTML markup, using 16

369
Index

Components (continued) Detecting

ID, local and global 14 data changes 186
isValid() 168 DOM
markup 11–12 external libraries 162, 166
methods 338 DOM access 135
modifying 169 DOM containment
namespace 13 proxy 136
overview 11 Dynamic output 26
styling 141, 144
styling with CSS 16 E
support level 11 errors 222, 226, 229
token 144 Errors
unescaping HTML 16 handling 172
using 78–79 throwing 172
validity 168 Event bubbling 105, 116
view 13 Event capture 105, 116
Conditional expressions 27 Event definitions
Controllers dependency 334
calling server-side actions 203, 205 Event handlers 187, 190
client-side 98 Events
creating 202 anti-patterns 127
server-side 202 application 111, 113–114, 117
Converters aura events 350
examples 318 aura:doneRendering 350
registering 317 aura:doneWaiting 351
Cookbook aura:event 335
Java 216 aura:locationChange 352
JavaScript 183 aura:systemError 352
CSS aura:valueChange 353
external 141, 333 aura:valueDestroy 354
tokens 144 aura:valueInit 355
custom 36 aura:valueRender 356
Custom Converters aura:waiting 356
examples 318 best practices 126
registering 317 bubbling 105, 116
capture 105, 116
D component 100, 102, 109
Data binding demo 121
expressions 27 example 109, 117
Data changes fire() 159
detecting 186 firing from non-Aura code 125
Dates flow 101, 112
JavaScript 193 getName() 159
Debugging getParam() 159
mode 262 getParams() 159
test assertions 255 getPhase() 159
user interactions 262 getSource() 159
DefDescriptor 218 handling 119
Detect data changes 353 pause() 159

370
Index

Events (continued)
preventDefault() 159
J
Java
propagation 101, 112
controllers 202
resume() 159
Java cookbook 216
setParam() 159
JavaScript
setParams() 159
access control 169
stopPropagation() 159
API calls 182
system 129
attribute values 157
system events 350
calling component methods 174, 176, 178
Events and actions 97
component 158
Examples
dates 193
converters 318
ES6 promises 180
Exceptions 215
events 159
Expressions
external 333
bound expressions 27
get() and set() methods 157
conditional 27
libraries 154
data binding 27
promises 180
dynamic output 26
secure wrappers 137, 139
format() 46
sharing code in bundle 152
functions 40
strict mode 134–135
operators 37
JavaScript API 139–140
tokens 148
JavaScript console 296
unbound expressions 27
JavaScript cookbook 183
External CSS 333
JSON 199
External JavaScript 333

F L
Label
format() 46
setting via parent attribute 49
G Label parameters 46
Labels
Global value providers 36
dynamically creating 47
globalID 32
JavaScript 47
H Libraries
JavaScript 154
Handling Input Field Errors 170
Lifecycle 169
Helpers 152
Lightning Container
HTML, supported tags
javascript 219
<a> 357
messaging 220, 224, 228
HTML, unescaping 16
Localization 51
I LockerService
global references 137, 139
Inheritance 240, 244
JavaScript API 140
Input Field Validation 170
secure wrappers 139
InstanceService 216
strict mode 135
Integration service 314–315
Log messages 296
Interfaces
marker 244 M
Introduction 1
Marks 306–307
isValid() 168
Markup 190

371
Index

Messaging Proxy object 136

notifications 343
overlays 343 Q
MetricsService Queueing
beacon 308 queueing server-side actions 206
beacons 306
example 308 R
logging 306 Reference
mark 309 doc app 323
marks 306–307 overview 322
transaction 309 Renderers 163, 213
transactions 304 Rendering 356
Mocking Rendering lifecycle 127
Java actions 288 Request
Java models 287 application 360
Java providers 288 Request lifecycle 359
overview 285 Rerendering 169, 356
Modal 345
Models S
Java 197 Secure wrappers
JSON 199 JavaScript API 139
Modes 290–291, 293–294 Security 134
Server-Side Controllers
N action queueing 206
Namespaces 13 calling actions 203, 205
Navigation, url-centric Source code 8
tokenized event attributes 240 States 205
Navigation,url-centric Storable actions
custom events 239 enable 210
Notices 343 lifecycle 209
Notifications 343 Storage service
adapters 245
O initializing 245
Object-oriented development Memory adapter 245
inheritance 240 SmartStore 245
Overlay 345 using 247
WebSQL 245
P Strict mode 135
Performance Styles 191
beacons 306 Styling
logging 306 join 141
marks 306–307 markup 141
transactions 304 readable 141
Performance warnings
<aura:if> 299 T
<aura:iteration> 300 Tags
Popover 345 <a> 357
Promises 180 anchor 357
Providers 166, 214 lightning:notificationsLibrary 343

372
Index

Tags (continued) ui components (continued)

lightning:overlayLibrary 345 inputPhone 62
Terminology 196 inputRadio 66
Ternary operator 27 inputRange 60
Testing inputRichText 62, 64
components 250 inputSearch 62
expect error 254 inputSecret 62
mode 250 inputSelect 69
pass an action 254 inputText 62
sample test cases 283 inputTextArea 62
Test setup 251 inputURL 62
Utility functions 262 list 76
Themes menu 72
vendor prefixes 142 menuItemSeparator 72
Toasts 343 menuTrigger 72
Tokens menuTriggerLink 72
bundles 145 message 71
configuration 144 outputCurrency 60
create 146 outputDate 59
define 146 outputDateTime 59
design 144 outputEmail 62
expressions 146, 148 outputNumber 60
using 147 outputPercent 60
Transactions 304 outputPhone 62
troubleshooting 222, 226, 229 outputRichText 62, 64
outputText 62
U outputTextArea 62
ui components outputURL 62
actionMenuItem 72 radioMenuItem 72
aura:component inheritance 54 vbox 73
autocomplete 74 ui components overview 58
block 72 ui events 57
button 67
checkbox 65 V
checkboxMenuItem 72 Value providers
inputCurrency 60 $Browser 33
inputDate 59 $Label 45
inputDateTime 59 Version numbers 3
inputDefaultError 71 versioning 24
inputEmail 62
inputNumber 60 W
inputPercent 60 Warnings 297

373