title: Custom Aspect Ratio with AutoLayout
body: <p>Let's say I have a UIView that contains a child UIView which has to be 4:3. I want to solve this problem using AutoLayout in code.  </p>
  
  <p>I've been struggling with AutoLayout but I haven't figured out yet how to do this.</p>
  
  <p>Do you know how to solve this problem?</p>
  
  <p>Thank you very much.</p>
  
  <p>I attach an image to explain better what I mean.
  <a href="http://d.pr/i/d0Oc" rel="noreferrer">http://d.pr/i/d0Oc</a></p>