title: _OBJC_CLASS_$ Error in iOS application
body: <p>"_OBJC_CLASS_$_AddViewController", referenced from:
        objc-class-ref-to-AddViewController in ContactsController.o</p>
  
  <p>ld: symbol(s) not found</p>
  
  <p>collect2: ld returned 1 exit status</p>
  
  <p>and the particular controllers are attached and compiling fine.</p>
  
  <p>Thanks</p>