title: What is a difference between self.view and self.view .superview of a rootViewController?
body: <p>I have a view controller which is assigned as a rootViewController like below :</p>
  
  <pre><code>self.viewCntrl = [[ViewController alloc]initWithNibName:@"ViewController" bundle:nil];
  self.window.rootViewController = self.viewCntrl;
  </code></pre>
  
  <p>And in the same view controller i have a button and i am performing transition animation on button click like this:</p>
  
  <pre><code>[UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view.superview cache:YES];
  </code></pre>
  
  <p>but it not works when i write like this:</p>
  
  <pre><code>[UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES];
  </code></pre>
  
  <p>As here self is a ViewController's object, the ViewController which is nothing but <strong>assigned to self.window.rootViewController</strong>. So why it takes self.view.superview instead of self.view to animate?</p>