title: _OBJC_CLASS_$_ - symbol(s) not found error
body: <p>I create a new application for iPad starting from an UISplitView application that works correctly, in the new application I get this error:</p>
  
  <pre><code>"_OBJC_CLASS_$_ConcertListController", referenced from:
  objc-class-ref-to-ConcertListController in RootViewController.o
  ld: symbol(s) not found
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>What it mean? How can I solve?</p>