Responder with generics

gistfile1.swift

//  A quick way to set up use of responder chain with a bit more type safety
//
//  Created by Patrick Lynch on 6/28/15.
//  Copyright © 2015 Patrick Lynch. All rights reserved.

import UIKit

protocol Responder {
	func targetForAction<T, U: RawRepresentable where U.RawValue == Selector>( action: U, withSender sender: AnyObject?) -> T
}

extension UIResponder : Responder {
	func targetForAction<T, U: RawRepresentable where U.RawValue == Selector>( action: U, withSender sender: AnyObject?) -> T {
		if let responder = self.targetForAction( action.rawValue, withSender: sender ) as? T {
			return responder
		}
		fatalError( "Unable to find responder in chain." )
	}
}

protocol FollowResponder {
	func followUser( completion:(()->())? )
	func unfollowUser( completion:(()->())? )
}

enum FollowAction: Selector {
	case FollowUser = "followUser:"
	case UnfollowUser = "unfollowUser:"
}

extension AppDelegate : FollowResponder  {
	
	func followUser( completion:(()->())? ) {
		print( "Following user..." )
		completion?()
	}
	
	func unfollowUser( completion:(()->())? ) {
		print( "Unfollowing user..." )
		completion?()
	}
}

class ViewController: UIViewController {
	
	@IBAction func onFollowButtonPressed( sender: AnyObject? ) {
		
		let responder: FollowResponder = self.targetForAction( FollowAction.FollowUser, withSender: self )
		responder.followUser {
			print( "User has been followed." )
		}
	}
}