Set rootViewController of UINavigationController by method other than initWithRootViewController

Question

How Do I set the rootViewController of UINavigationController by a method other than initWithRootViewController?

I want use

Answer 1

  let storyboard = UIStoryboard(name: "Main", bundle: nil)         
  let yourNewRootView = storyboard.instantiateViewControllerWithIdentifier("yourNewRootView") as? yourNewRootView


   self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

    UIView.transitionWithView(self.window!, duration: 0.1, options: [UIViewAnimationOptions.TransitionFlipFromRight,UIViewAnimationOptions.TransitionFlipFromLeft], animations: 
    {
        // animation

        }, completion: { (finished: Bool) -> () in

            self.window?.rootViewController = nil
            self.window?.rootViewController = yourNewRootView
            self.window?.makeKeyAndVisible()
    })