title: Set Initial view controller with tab bar and nav bar
body: <p>I have a tab bar controller as my initial view controller in storyboard (with the arrow). However when a user signs in the first time, I'm trying to change the initial view controller programmatically in <code>didFinishLaunchingWithOptions:</code> to start out at a navigation controller to go through a couple VCs for them to enter signup information (I don't want a tab bar for this). Although I'm changing the initial VC in my app delegate, I'm getting a crash with <code>Could not cast value of type 'UITabBarController' (0x1031374f8) to 'UINavigationController' (0x1031374a8).</code> I was under the impression that the initial VC would be changed and not reference the Tab Bar Controller at all? Is there a way I can accomplish changing the initial VC without the Tab Bar Controller being referenced? Here is my code in <code>didFinishLaunchingWithOptions:</code>, any help is GREATLY appreciated!</p>
  
  <pre><code>  if User.current() == nil {
       let storyboard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
       let navigationControllerr:UINavigationController = storyboard.instantiateInitialViewController() as! UINavigationController
       let initialViewController = storyboard.instantiateViewController(withIdentifier: "SplashPageVC")
       navigationControllerr.viewControllers = [initialViewController]
       self.window?.rootViewController = navigationControllerr
    }
  </code></pre>