title: Set AutoLayout Size Class Programmatically?
body: <p>With iOS 8 and Xcode 6, in storyboards we now have the screen size grid letting us select a size class. Where you can select layout formatting for the different screen sizes.</p>
  
  <p>I have found this brilliantly helpful, as it allows me to set the base constraints and then unique ones for each screen size.</p>
  
  <p>My question is, can you do this programmatically? I create my <code>NSLayoutConstraint</code> as normal but I need to be able to specify different constraints for different screen sizes.</p>