title: Distinguish iPad orientation with size classes
body: <p>With iOS 8 Apple introduced <em>size classes</em> for handling layouts of an app. Instead of designing user interfaces dependent on device, screen size, and orientation, developers are encouraged to rather adapt their app's layout depending on the active size classes. That's a good move, I think.</p>
  
  <p>However, when it comes to the iPad there seem to be no way to distinguish the different device orientations (which provide quite different screen space and handling in my opinion). From the <a href="https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/LayoutandAppearance.html" rel="nofollow noreferrer">Human Interface Guidelines</a>:
  <img src="https://i.stack.imgur.com/YKLoi.png" alt="iPad Size Classes">
  What am I supposed to do now if I want to present a side menu only in landscape orientation because it provides more space, like a <code>UISplitViewController</code>?</p>
  
  <p>Is the <code>UISplitViewController</code> another case where Apple doesn't eat it's own dog food and uses some other metrics like the device orientation or the actual screen width to determine the layout? Or is there another, official way to do that? Something I could do in Interface Builder alone without code?</p>
  
  <p>(And no, I don't want to use <code>UISplitViewController</code> for several reasons.)</p>