Gamecenter代码根本不起作用，总是打印错误。

Question

我正在学习如何将Gamecenter放入应用程序，使用Xcode，Swift和SpriteKit。每当我玩iOS模拟器时，都不会弹出任何内容（要么弹出＆＃34;登录＆＃34;屏幕应该弹出，或者＃34;欢迎回来＆＃34;屏幕应该弹出）并且控制台打印＆ ＃34;假＆＃34 ;.我一直想弄清楚它为什么不起作用。 （哦，如果这有帮助，我现在正在为El Capitan运行OS X Beta）有人请帮忙！

以下是代码：

import GameKit

类ViewController：UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()

    authenticateLocalPlayer()



    // Do any additional setup after loading the view, typically from a nib.
}


func authenticateLocalPlayer(){


    var localPlayer = GKLocalPlayer.localPlayer()
    localPlayer.authenticateHandler = {(viewController, error) -> Void in

        if (viewController != nil) {
            //These 2 lines are the only parts that have been changed
            let vc: UIViewController = self.view!.window!.rootViewController!
            vc.presentViewController(viewController, animated: true, completion: nil)
        }
        else {
            println((GKLocalPlayer.localPlayer().authenticated))
        }
    }
}




override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}