Swift 重置NSUserDefault后显示ViewController

我有一个重置按钮，重置所有NSUserDeafolts，然后重新加载到NavigationController的第一个游戏

//Reset the NSUserdefault saved objects (No problems here)
let appDomain : NSString = NSBundle.mainBundle().bundleIdentifier!
            NSUserDefaults.standardUserDefaults().removePersistentDomainForName(appDomain)
            println("button pressed")

//Present first ViewController (Having problems in this code)
let storyboard = UIStoryboard(name: "Main", bundle: nil);

let mainViewController:ViewController = ViewController()

presentViewController(mainViewController, animated: true, completion: nil)

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你必须这样做-但我有一些问题，当使用这个稍后。。。叹息

我希望我知道这样重置视图的正确方法-但是我找不到任何信息

           let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
            var setViewController = mainStoryboard.instantiateViewControllerWithIdentifier("GameViewController") as! UIViewController
            var vc = self.view?.window?.rootViewController
            vc?.presentViewController(setViewController, animated: true, completion: nil)

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你犯了什么错误？添加更多信息。我没有发现错误。但是当我按下按钮的时候。我有一个空白的黑屏