title: Swapping rootViewController with animation
body: <p>I'm having a little trouble swapping rootViewControllers with animation. Here's the code that I'm using:</p>
  
  <pre><code>[UIView transitionWithView:self.window duration:0.8 options:UIViewAnimationOptionTransitionFlipFromRight animations:^{
          self.window.rootViewController = self.navigationController;
      } completion:nil];
  </code></pre>
  
  <p>It kind of works except that right before the animation, the screen turns to black and then the animation occurs. It looks like the original rootViewController is getting removed right before the animation. Any ideas?</p>