Ruby On Rails
CSCI 5449
Submitted by: Bhaskar Vaish
What is Ruby on Rails ?
Ruby on Rails is a web application framework
written in Ruby, a dynamic programming
language.
Ruby on Rails uses the Model-View-Controller
(MVC) architecture pattern to organize application
programming.
What is Ruby on Rails ?(Continued)
• A model in a Ruby on Rails framework maps to a
table in a database
• A controller is the component of Rails that responds
to external requests from the web server to the
application, and responds to the external request by
determining which view file to render
• A view in the default configuration of Rails is an erb
file. It is typically converted to output html at run-
time
Ruby
• It is a dynamic, general-purpose object-oriented
programming language
• Combines syntax inspired by Perl, also influenced
by Eiffel and Lisp
• Supports multiple programming paradigms,
including functional, object oriented, imperative
and reflective
Ruby(Contd.)
• Has a dynamic type system and automatic
memory management
• Ruby is a metaprogramming language.
Sample Ruby Code
# Output “Bhaskar”
puts “Bhaskar”
# Output “Bhaskar” in upprecase
puts “Bhaskar”.upcase
# Output “Bhaskar” 10 times
10.times do
puts “Bhaskar”.upcase
end
Sample Ruby Code: Class
Class Employee: defining three attributes for a
Employee; name, age, position
class Employee # must be capitalized
attr_accessor :name, :age, :position
# The initialize method is the constructor
def initialize(name, age, position)
@name = name
@age = type
@position = color
end
New Employee
Creating an instance of the Employee class:
a = Employee.new(“JAY", “23", “Test Engineer")
b = Employee.new(“SAM", “24", “Test Engineer")
Method
To be able to describe employees, we add a method
to the employee class:
def describe
@name + " is of " + @age + " years"
+" working as "
+ @position+ ".\n"
end
Calling Method
To get the description of Employee, we can call
Employee with the describe method attached :
emp= a.describe
puts emp
or:
puts a.describe
Rails
• Rails is an open source Ruby framework
for developing database-backed web
applications
• The Rails framework was extracted from
real-world web applications. Thus it is an
easy to use and cohesive framework that's
rich in functionality
Rails(Contd.)
• All layers in Rails are built to work together
and uses a single language from top to
bottom
• Everything in Rails (templates to control
flow to business logic) is written in Ruby,
except for configuration files - YAML
What is so special about Rails
• Other frameworks use extensive code
generation, which gives users a one-time
productivity boost but little else, and
customization scripts let the user add
customization code in only a small number of
carefully selected points
• Metaprogramming replaces these two primitive
techniques and eliminates their disadvantages.
• Ruby is one of the best languages for
metaprogramming, and Rails uses this capability
well.
What is so special about Rails
Scaffolding
• You often create temporary code in the early
stages of development to help get an application
up quickly and see how major components work
together. Rails automatically creates much of the
scaffolding you'll need.
What is so special about Rails
Convention over configuration
• Most Web development frameworks for .NET or Java
forces to write pages of configuration code, instead Rails
doesn't need much configuration. The total configuration
code can be reduced by a factor of five or more over
similar Java frameworks just by following common
conventions.
• Naming your data model class with the same name as
the corresponding database table
• ‘id’ as the primary key name
What is so special about Rails
Active Record framework
• Saves objects to the database.
• Discovers the columns in a database schema
and automatically attaches them to domain
objects using metaprogramming.
What is so special about Rails
Action Pack
• Views and controllers have a tight interaction, in rails
they are combined in Action Pack
• Action pack breaks a web request into view components
and controller compoents
• So an action usually involves a controller request to
create, read, update, or delete (CRUD) some part of the
model, followed by a view request to render a page
Rails implements the model-view-
controller (MVC) architecture.
Model View Contoller (MVC)
The MVC design pattern separates the component
parts of an application
MVC pattern allows rapid change and evolution of
the user interface and controller separate from the
data model
Model
• Contains the data of the application
• Transient
• Stored (eg Database)
• Enforces "business" rules of the application
• Attributes
• Work flow
View
• Provides the user interface
• Dynamic content rendered through templates
• Three major types
• Ruby code in erb (embedded ruby) templates
• xml.builder templates
• rjs templates (for javascript, and thus ajax)
Controller
• Perform the bulk of the heavy lifting
• Handles web requests
• Maintains session state
• Performs caching
• Manages helper modules
Creating a Simple Application
Requirements
• Ruby
• RubyGems
• Rails
• SQlite, PostGres or MySQL
• I will be developing on Windows 7
I have created an application which can be
accessed at
http://ancient-ridge-9795.herokuapp.com/
It consists of a Home page which displays text
And has two right and left buttons, which can
be used for displaying and adding messages.
Steps Involved
Creating application on the local host
Step 1: On the Terminal type:
rails new yourapp_name #webpage in my case
hit enter, we see the scripts flow in the terminal creating a bunch of files
Step 2: Change the directory to the
application
cd webpage
These are the files which rails automatically generates to create the
framework for our application.
Step 3:
Create the needed controller, model and views
for our application
I will keep simple functionality in which a user
can post message
$rails generate scaffold post name:string address:text
• Scaffold command creates a CRUD (Create, Read,
Update, Delete) interface for app ( a quick way of
creating the MVC automatically).
• Alternatively, we can also create our controller,
model and view manually using the command
// for creating controller
rails generate controller <controller name>
// for creating model
rails generate model <model name>
Step 4:
Create Database
rake db:create
The figure shows the database.yml file created
Step 5:
Since we have recently created a new model
for Post, a table must be created in our
database and requires that we upgrade the
database using this command:
rake db:migrate
Step 5:
Creating a home page
$rails generate controller home index
This creates a controller “home” along with views in
the app/view/home directory. Rails will create several
files for you, including app/views/home/index.html.erb
file. This is the template that we will use to display the
results of the index action (method) in the home
controller. Open this file in your text editor and edit it
to contain the code that you want to display in your
index page
Editing homepage
Open file app/views/home/index.html.erb and edit
it to contain the code that you want to display in your
index page
Step 6: Rails Routing
Edit config/routes.rb
The See Messages and Write Messages will appear on the main page
Step 7: Text on the page
Edit the index.html file, enter text which will
appear on the screen
The See Messages and Write Messages will appear on the main page
Step 8: Set Background images and color
Edit the home.css file, to set background image
and text color
The See Messages and Write Messages will appear on the main page
Step 8: Testing the application
On the command line enter
rails server
The application will be uploaded to
http://localhot:3000/
References:
• ppt, Ruby on Rails, A new gem in web development
• ppt, Ruby Intro
• Ruby on Rails tutorial book
http://en.wikipedia.org/wiki/Ruby_on_Rails
http://fuelyourcoding.com/creating-your-first-
ruby-on-rails-application-from-scratch/
