title: Size classes with xib files not working
body: <p>Currently, I'm working on universal app (iPhone / iPad) supported on iOS 7 &amp; iOS 8.</p>
  
  <p>Here is my problem regarding size classes :</p>
  
  <ol>
  <li><p>My navigation bar is defined into a XiB file (NavBarView.xib)</p></li>
  <li><p>Inside this file, I have a UIButton that I want to display only on iPhone mode, and a UISearchBar only for iPad mode.</p></li>
  <li><p>To handle that whitout any line code, I used the new feature "Use size classes" available for views since iOS 8. I defined "size classes" for these two elements inside my XiB file.</p>
  
  <ul>
  <li><p>UISearch for Ipad : Installed for all layouts except Compact Width / Any Height (wC hAny)</p></li>
  <li><p>UIButton fo Iphone : Not installed for all layouts but with Compact Width / Any Height (wC hAny)</p></li>
  </ul></li>
  </ol>
  
  <p>This mechanism works pretty fine on iOS 8 for iphone and ipad, but not on iOS 7. However, if I apply these size classes direclty into views contained into the storyboard, it works for iOS 7.</p>
  
  <p>Could anyone explain me why my size classes are not working when they are defined into XiB files on iOS 7 ?</p>
  
  <p>Best Regards and many thanks,</p>
  
  <p>Lorenzo.</p>