Question

我有一个名为Attendee的类，它继承自PFObject。在我的applicationDidFinishLaunching()方法中，我像这样注册子类：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    Attendee.initialize()
    Parse.enableLocalDatastore()
    Parse.setApplicationId(ObjectManager.appID, clientKey: ObjectManager.clientKey)

    getData()

    return true
}

func getData() {
    //create the query
    var attendeeQuery = Attendee.query()
    attendeeQuery?.fromLocalDatastore()
        .fromPinWithName(CacheKeys.AttendeesKey)
        .whereKey("conference", equalTo: ObjectManager.currentConf)

    //register a background task
    var bgTask = UIBackgroundTaskInvalid
    bgTask = UIApplication.sharedApplication().beginBackgroundTaskWithExpirationHandler({ () -> Void in
        UIApplication.sharedApplication().endBackgroundTask(bgTask)
        bgTask = UIBackgroundTaskInvalid

        println("Attendees Loader Expiration Handler called")
    })

    //run the query
    attendeeQuery?.findObjectsInBackgroundWithBlock({ (cachedAttendees: [AnyObject]?, error:NSError?) -> Void in
        if error != nil {
            println(error)
            return
        }

        ...

            UIApplication.sharedApplication().endBackgroundTask(bgTask)
        })
    })
}

但是，当我运行代码时，我在行var attendeeQuery = Attendee.query()处得到一个例外。例外情况说我需要在使用它之前注册Attendee子类。我不明白为什么会这么说，因为我事先注册了。以下是Attendee类定义。

class Attendee: PFObject, PFSubclassing {

    var name:String
        {
            return self["name"] as! String
    }

    ...

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

    class func parseClassName() -> String {
        return Classes.Attendee
    }
}

例外：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'The class MedConf.Attendee must be registered with registerSubclass before using Parse.'
*** First throw call stack:
(0x1835002d8 0x194d240e4 0x183500218 0x1001e21d0 0x1001e1fac 0x100135d88 0x100138af0 0x1000e43e0 0x1000e4580 0x187fb3190 0x1881ca854 0x1881cd208 0x1881cb778 0x18bd093c8 0x1834b827c 0x1834b7384 0x1834b59a8 0x1833e12d4 0x187fac43c 0x187fa6fac 0x1000e7b48 0x1953a2a08)

Answer 1

当我从1.6.3升级到Parse的iOS SDK 1.7.5时，我遇到了同样的问题。问题出在我的初始化函数中，看起来和你的一样。

将dispatch_once_t用作函数中的局部变量不能用于确保子类只注册一次;我注意到在initialize函数中的registerSubclass（）调用上放了一个断点，它被多次调用。不断重新注册子类显然会导致新版Parse SDK出现问题。

将初始化函数更改为这样可以解决问题：

private static var onceToken : dispatch_once_t = 0

override class func initialize() {
    dispatch_once(&onceToken) {
        self.registerSubclass()
    }
}

Answer 2

如何跟踪must be registered with registerSubclass

错误

因此，您需要调用registerSubclass方法而不是initialize

所以这里是代码：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    Attendee.registerSubclass()
    Parse.enableLocalDatastore()
    Parse.setApplicationId(ObjectManager.appID, clientKey: ObjectManager.clientKey)

    getData()

    return true
}

使用Parse注册子类时出现异常

2 个答案: