PFObject Subclasses in Swift

So with the new Swift programming language came a whole lot of improvements to the development workflow. It also came with a lot of headaches, of which I will demonstrate right now.

I am making an app where I want to use Parse as a backend. Thus, I decided I needed to subclass PFObject to make my data model come to life. As you've probably seen online, there has been a lot of trouble trying to get this to work in Swift, so I offer my solution to you all:

//
//  API.swift
//
//  Created by Matthew Wyskiel on 10/21/14.
//  Copyright (c) 2014 Matthew Wyskiel. All rights reserved.
//

import UIKit
import Parse

public class API: PFObject, PFSubclassing {

    override public class func load() {
    	registerSubclass()
    }

    public class func parseClassName() -> String! {
    	return "API"
    }

    @NSManaged public var name: String!
    @NSManaged public var url: String!
    @NSManaged public var icon: PFFile!
    @NSManaged public var descriptionString: String!
    @NSManaged public var supportURLs: [NSString: String]!
    @NSManaged public var librariesURLs: [NSString: String]!

}

Firstly you may notice that I can just import Parse as I can a system framework. This is because Parse included a .modulemap file in their framework in order for it to become modularized, so it will work as an Objective-C Module. I love this a lot because I can just Option-Click a class name (such as PFFile) and immediately see the public methods in Swift format, just like system headers!

Let's see how I made this happen!

###1. Import Parse, Subclass PFObject, and conform to PFSubclassing This is a fairly straightforward step as it just involves adding an import and editing the class hierarchy:

###2. Override required PFSubclassing methods This is made easier for you by the framework: there are originally 5 reqired methods for override of a class that conforms to PFSubclassing, but PFObject already implements 3 of those 4 of those methods; all you need to implement is parseClassName():

Then you need to "register" the class with the Parse SDK. It's best to do this before the setApplicationKey() call in the app delegate. The best way you can do this is by overriding the class function load():

Great. No Swift interference, right? Well, it's coming.

###3. Add your properties Now, the Parse docs want us to use the @dynamic keyword when using Objective-C. However, the dynamic attribute in Swift is different from @dynamic. The closest Swift equivalent for @dynamic is @NSManaged, which the Apple documentation claims is reserved for Core Data. I beg to differ because it works for what Parse wants to do. I just didn't realize it until I tried it.

##Yay! Put together, you get a darn good class. And it works too; just try it with your Parse app. Hope this helps confusion!

##Note If you use Parse in your app as well as in an internal framework used for your app, you need to call setApplicationKey() in both targets (I learned that the hard way.) The way I handled this is by creating an initialize() class method in the principal class of the framework:

Then I call this method in my app delegate as well as the setApplicationId() method, and everything just works!!

Update: With Swift 1.2 and later, overriding load() causes a build error because that function was associated with Objective-C (try it; that's actually the error). so just change load to initialize (which does practically the same thing) and it should work just fine.