title: Performance of UIView: removeFromSuperview VS hide
body: <p>This question is really basic. What is the performance difference between removing a <code>UIView</code> from the view hierarchy and hiding a <code>UIView</code>?</p>
  
  <p>I have read that Views that are not needed should be removed from the view hierarchy. I currently have the situation that a <code>UIButton</code> should sometimes be visible. When do I hide the <code>UIButton</code> and when do I remove it from it's superview?</p>
  
  <p>Is it expensive to change the view hierarchy?  </p>