Sample code for blog.
Includes helper library to discover Apex Interface implementaitons and Actions.
// Use Extensions.find to get all ICalculatorFunctions implementations
Extensions.ApexExtensionsFindResults results =
new Extensions().find(ICalculatorFunctions.class);
List various types of Actions
// Find all Flow custom actions
List<Extensions.ActionExtensionsFindResult> flowActions =
new Extensions().find(Extensions.ActionTypes.FLOW);