在iOS上更改初始屏幕

Question

我试图将登录屏幕添加到我的应用程序，但是当我尝试将初始视图控制器更改为登录屏幕时，但是当我更改初始视图控制器指针时，它没有任何作用。 我已经尝试过以下建议：

iOS 7-无法实例化默认视图控制器，但它们对我不起作用。 相反，导航控制器下的第一个屏幕显示的是添加登录名之前的预期初始视图。

应用程序委托

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)

    let centerViewController = mainStoryboard.instantiateViewControllerWithIdentifier("ViewController") as!ViewController

    let drawerViewController = mainStoryboard.instantiateViewControllerWithIdentifier("DrawerViewController") as!DrawerViewController

    let leftSideNav = UINavigationController(rootViewController: drawerViewController)
    let centerNav = UINavigationController(rootViewController: centerViewController)

    centerContainer = MMDrawerController(centerViewController: centerNav, leftDrawerViewController: leftSideNav)

    centerContainer!.openDrawerGestureModeMask = MMOpenDrawerGestureMode.PanningCenterView;
    centerContainer!.closeDrawerGestureModeMask = MMCloseDrawerGestureMode.PanningCenterView;

    //works when i comment out this but navigation does not work then
    //window!.rootViewController = centerContainer
    window!.makeKeyAndVisible()



    return true
}