title: Centering with Auto layout Xcode
body: <p>I'm developing a swift app, and I am designing the interface in interface builder in Xcode. My interface (which consists of two UILabels, looks fine in portrait mode, but looks awful in landscape mode.</p>
  
  <p>The issue is that the labels won't stay centered, as I want them, when rotated. I used the following auto layout constraints:</p>
  
  <pre><code>Upper edge constraint: top layout guide 
  Lower edge constraint: bottom layout guide
  Right edge constraint: standard value
  Left edge constraint: standard value
  </code></pre>
  
  <p>These settings must not be working, as the label doesn't stay centered when rotated. What are the proper constraints to use for auto layout to center this label?</p>