custom_transforms_closures.md

##Example - Closure Transformations

As of version 0.2.0 of U2MapperKit, the ability to map closures via the US2TransformerProtocol as support was added. This ensures that we can return an a value of Any type. Let's look at a dictionary for a business object, and see how we can map a function/closure.

Response Dictionary

{
	'business_uuid'  	 		:  9223123456754775807,
	'business_name'  			: 'UsTwo Restaurant',
	'business_facebook_id'  	: '123456789323123',
	'business_yelp_id'  		: '409283409238409',
}

Let's create a mapper that parses out the values from the response which, based on the identifier, returns the clousure:

US2ExampleSocialClosureTransformer Implementation

import Foundation
import UIKit

let facebookIDKey = "facebook_id"
let yelpIDKey     = "yelp_id"

public class US2ExampleSocialClosureTransformer : US2TransformerProtocol {

    public func transformValues(inputValues : Dictionary<String, Any>?) -> Any? {
        if let facebookdentifier = inputValues![facebookIDKey] as? String {
       		func routeToFacebookApp() {
    			if UIApplication.sharedApplication().openURL(NSURL(string:"fb://")!) {
       				let facebookAppLink = "fb://profile/\(facebookdentifier)"
        			UIApplication.sharedApplication().openURL(NSURL(string: facebookAppLink)!)
    			} else {
        			let itunesLink = "itms://itunes.apple.com/us/app/apple-store/id284882215?mt=8"
        			UIApplication.sharedApplication().openURL(NSURL(string: itunesLink)!)
    			}
			}
            return routeToFacebookApp
        }
        
        if let yelpIdentifier = inputValues![yelpIDKey] as? String {
            
            func routeToFacebookApp() {
    			if UIApplication.sharedApplication().openURL(NSURL(string:"yelp://")!) {
        			let yelpAppLink = "yelp:///biz/\(yelpIdentifier)"
        			UIApplication.sharedApplication().openURL(NSURL(string:yelpAppLink)!)
    			} else {
        			let itunesLink = "itms://itunes.apple.com/us/app/apple-store/id284910350?mt=8"
        			UIApplication.sharedApplication().openURL(NSURL(string: itunesLink)!)
   				 }
			}
			
            return routeToYelpApp
        }
        return nil
    }
}

Now that we have created a transformer, let's create some mapping to map our closures to an isntance variable.

Business.plist

After the creation of the mapping, perform a build (⌘-B). The changes should be reflected accordingly in the internal _Business.swift class.

import Foundation
import US2MapperKit

class _Business {
	var uuid : Double?
	var name : String?
	var routeToFacebook : (() -> Void)?
	var routeToYelp : (() -> Void)?

 	required init() {...}

 	convenience init?(_ dictionary: Dictionary<String, Any>) {...}
} 

After calling the fail-able initializer - or udpateWithDictionary method with a dictioanry representation - US2MapperKit will use the custom transformer to map the custom closure accordingly. Although this is a simple and abstract scenerio, the potential for this funtionality has many outcomes to be explored.

Note: The the keys defined in the property mapping correspond to the keys in the dictionary of values passed to the public func transformValues(inputValues : Dictionary<String, Any>?) -> Any? method defined by the protocol.