title: When the autolayout constraints set frames during view controller life cycle?
body: <p>I have used autolayout constraints from storyboard. However in some cases, I want to calculate dynamic height of subview. I code this in viewDidAppear(), it works fine because this method is called after all view frames are set by layout constraints. The problem here is that I can see the frame set by constraints for half a second. And then the code reframes the view. </p>
  
  <p>I came to know about viewDidLayout() which is called after constraints has set the frame so I can change. But it doesn't work. It is like this method is called before constraints are used.</p>