title: UIView flip transition with show hide animation iOS
body: <p>I'm making flip animation from one UIView to another, which is behind first one and hidden. 
  code: </p>
  
  <pre><code>UIView.transition(from: mediumFirstView, to: mediumSecondView, 
                    duration: 0.5, options: [.transitionFlipFromRight, 
                                             .showHideTransitionViews]) { _ in
      self.mediumFirstView.isUserInteractionEnabled = false
      self.mediumSecondView.isUserInteractionEnabled = true
  }
  </code></pre>
  
  <p>or this: </p>
  
  <pre><code>UIView.transition(with: mediumLimitedView, duration: 0.5, 
                    options: [.transitionFlipFromRight, 
                              .showHideTransitionViews], 
                    animations: {
      self.mediumFirstView.alpha = 0
      self.mediumSecondView.alpha = 1
  }) { _ in
      self.mediumFirstView.isUserInteractionEnabled = false
      self.mediumSecondView.isUserInteractionEnabled = true
  }
  </code></pre>
  
  <p>Problem of both is that First UIView becomes hidden only after full animation of flip, not on half as expected. Am I doing something wrong? </p>
  
  <p>Views hierarchy:</p>
  
  <p><a href="https://i.stack.imgur.com/o6PJX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o6PJX.png" alt="Views hierarchy"></a></p>