在我的GameScene.swift文件中，我试图像下面这样对我的菜单视图控制器执行一次segue：

func returnToMainMenu(){
    var vc: UIViewController = UIViewController()
    vc = self.view!.window!.rootViewController!
    vc.performSegueWithIdentifier("menu", sender: vc)
}

点击节点时运行此方法：

override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {
    for touch: AnyObject in touches {
        let location = touch.locationInNode(self)
        if gameOn == false{
            if restartBack.containsPoint(location){
                self.restartGame()
            }
            else if menuBack.containsPoint(location){
                self.returnToMainMenu()
            }
            else if justBegin == true{
                self.restartGame()
            }
        }
    }
}

menuBack返回菜单的按钮在哪里。每次运行此代码时，都会引发NSException：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Receiver (<ProxyBlock.Menu: 0x165a3e90>) has no segue with identifier 'menu''

我检查了segue的标识符，它的确是“菜单”。