Parse PFSubclassing not working with Swift

Question

I have copied the Parse Swift example for Subclassing:

class Armor : PFObject, PFSubclassing {

    override class func load() {
        self.registerSubclass()
    }
    class func parseClassName() -> String! {
        return "Armor"
    }
}

I get the following errors:

/Parse/Armor.swift:11:1: error: type 'Armor' does not conform to protocol 'PFSubclassing'
class Armor : PFObject, PFSubclassing {
^
__ObjC.PFSubclassing:15:28: note: protocol requires function 'object()' with type '() -> Self!'
  @objc(object) class func object() -> Self!
                           ^
__ObjC.PFSubclassing:23:52: note: protocol requires function 'objectWithoutDataWithObjectId' with type '(String!) -> Self!'
  @objc(objectWithoutDataWithObjectId:) class func objectWithoutDataWithObjectId(objectId: String!) -> Self!
                                                   ^
__ObjC.PFSubclassing:30:27: note: protocol requires function 'query()' with type '() -> PFQuery!'
  @objc(query) class func query() -> PFQuery!
                          ^
__ObjC.PFSubclassing:35:38: note: protocol requires function 'registerSubclass()' with type '() -> Void'
  @objc(registerSubclass) class func registerSubclass()
                                     ^
/Parse/Armor.swift:14:9: error: 'Armor.Type' does not have a member named 'registerSubclass'
        self.registerSubclass()
        ^    ~~~~~~~~~~~~~~~~

I saw this answer: https://stackoverflow.com/a/24899411/843151 and tried that solution with no luck, I get the same errors.

Any suggestions of why this is happening? Thanks in advance.

Answer 1

我需要在Objective-C桥接头中导入解析PFObject + Subclass.h

#import <Parse/PFObject+Subclass.h>

Answer 2

With xCode 6.1.1 I was able to get this working without the bridging header. Just:

import Parse 

at the top of the module. For the class declaration I did need to use @NSManaged for the variable types to get them to link to the Parse class variables successfully. Like this:

class PSCategory : PFObject, PFSubclassing {
    override class func load() {
        self.registerSubclass()
    }
    class func parseClassName() -> String! {
        return "Category"
    }

    @NSManaged var Name: String
}

Then in my query all the names are dynamically linked:

var query = PSCategory.query() // PFQuery(className: "Category")

query.cachePolicy = kPFCachePolicyCacheElseNetwork // kPFCachePolicyNetworkElseCache
query.maxCacheAge = 60 * 60 * 24  // One day, in seconds.
query.findObjectsInBackgroundWithBlock {
    (categories: [AnyObject]!, error: NSError!) -> Void in
    if error == nil {
        for abstractCategory in categories {
            let category = abstractCategory as PSCategory

            NSLog("Category Name: %@", category.Name)
        }
    } else {
        NSLog("Unable to retrieve categories from local cache or network")
    }
}

Answer 3

Parse recommends initialize() instead of load()

class Armor : PFObject, PFSubclassing {
  override class func initialize() {
    var onceToken : dispatch_once_t = 0;
    dispatch_once(&onceToken) {
      self.registerSubclass()
    }
  }

  static func parseClassName() -> String! {
     return "Armor"
  }
}

Answer 4

It appears that PFSubclassing does not currently work correctly in Swift as is, as of v1.7.2, released April 27, 2015.

I was able to get it working by implementing custom getters and setters for properties as a temporary workaround--which somewhat defeats the purpose, but at least this approach will result in only minor refactoring once PFSubclassing is made ready for Swift.

It is not necessary to add #import <Parse/PFObject+Subclass.h> to the bridging header. But, as indicated in the PFSubclassing Protocol Reference, " Warning: This method must be called before [Parse setApplicationId:clientKey:] ," you should register all PFObject custom subclasses before calling Parse.setApplicationId(_:, clientKey:) .

Here's an example for a custom PFObject subclass called PFChatLOCMessage:

// In ProjectName-Bridging-Header.h
#import <Parse/Parse.h>

// In AppDelegate.swift
@UIApplicationMain
final class AppDelegate: UIResponder, UIApplicationDelegate {

  func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    configureParse()
    return true
  }

  func configureParse() {
    registerParseSubclasses()
    Parse.setApplicationId("...", clientKey: "...")
  }

  func registerParseSubclasses() {
    PFChatLOCMessage.registerSubclass()
  }

}

// In PFChatLOCMessage.swift
private let PFChatLOCMessageClassName = "PFChatLOCMessage"
private let userKey = "user"

class PFChatLOCMessage: PFObject {

  var user: PFUser! {
    get { return self[userKey] as! PFUser }
    set { self[userKey] = newValue }
  }

  override init() {
    super.init()
  }

  override init(user: PFUser) {
    super.init()
    self.user = user
  }

}

extension PFChatLOCMessage: PFSubclassing {

  class func parseClassName() -> String {
    return PFChatLOCMessageClassName
  }

}

Answer 5

I got deadlocks / hangs using override class func initialize - even though that's recommended in the parse documentation.

Thinking about it, it's not a good idea to do threading in the init methods of classes - you never know when or in what context these might get called.

This worked for me - for all my custom subclasses, before I call the parse init methods, I explicitly register them as subclasses.

This way the order in which things get called is well defined. Also, it works for me ;)

    MyPFObjectSubclass.registerSubclass()
    MyPFObjectSubclass2.registerSubclass()
    MyPFObjectSubclass3.registerSubclass()
    // etc...

    let configuration = ParseClientConfiguration {
        $0.applicationId = "fooBar"
        $0.server = "http://localhost:1337/parse"
    }
    Parse.initializeWithConfiguration(configuration)