ios - 解析查询在重启时返回 PFObject 而不是子类

Question

我有以下 PFObject 子类:

class Show: PFObject, PFSubclassing {

    @NSManaged var date: NSDate

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

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

然后我可以添加新的 Show 对象，如下所示:

let newShow = Show()
newShow.date = NSDate()
newShow.pinInBackground()

并查询Show对象。

let query = Show.query()!
query.fromLocalDatastore()
query.orderByAscending("date")
query.findObjectsInBackgroundWithBlock { (shows, error) -> Void in

    println("shows:\(shows)")

    let myShows = shows as? [Show]

    println("myShows:\(myShows)")

    let myObjects = shows as? [PFObject]

    println("myObjects:\(myObjects)")
}

按预期返回 [Show]:

shows:Optional([<Show: 0x7fde6a8ba0f0, objectId: new, localId: local_90293157b4a20c5c> {
    date = "2015-06-01 12:08:16 +0000";
}])

myShows:Optional([<Show: 0x7fde6a8ba0f0, objectId: new, localId: local_90293157b4a20c5c> {
    date = "2015-06-01 12:08:16 +0000";
}])

myObjects:Optional([<Show: 0x7fde6a8ba0f0, objectId: new, localId: local_90293157b4a20c5c> {
    date = "2015-06-01 12:08:16 +0000";
}])

但是，如果我终止应用，然后重新运行相同的查询，结果数组是[PFObject] 而不是[Show]

shows:Optional([<Show: 0x7fef632ca2b0, objectId: new, localId: local_c6995edd73e73e10> {
    date = "2015-06-01 12:08:16 +0000";
}])

myShows:nil

myObjects:Optional([<Show: 0x7fef632ca2b0, objectId: new, localId: local_c6995edd73e73e10> {
    date = "2015-06-01 12:08:16 +0000";
}])

我错过了什么吗？为什么在重新启动应用程序后没有返回正确类的对象？

Answer 1

好的，所以我在 Root View Controller 的 viewDidLoad 方法中运行查询。检查 registerSubclass 的 PFSubclassing 文档:

@warning This method must be called before <[Parse setApplicationId:clientKey:]>

根据 Parse 文档中的示例，我重写了 initialize 方法，但是在创建查询时会调用此方法，但会在调用 appDidFinishLaunching 方法之前调用 setApplicationId:clientKey

所以关键是稍后运行查询，或者更早地注册子类!