title: How to get real size UIView with autolayout
body: <p>I'm a new developer iOS.</p>
  
  <p>I use auto-layout.</p>
  
  <p>I have a problem. I can not get real size of UIView after constraints.</p>
  
  <p>Example, when I want get size of <code>UIView</code> with constraint</p>
  
  <pre><code>self.container.frame.size.height
  </code></pre>
  
  <p>It alway return 550 for all device size. But I can see it have difference size when I run it on difference device.</p>
  
  <p>Thanks</p>