title: Xcode extensions class call method: sigabrt
body: <p>I have a strange problem ...
  I have two projects in Xcode: PR1 and PR2. PR2 is linked in PR1.
  In the PR2 i have class and some "extensions class". In PR1 i use some extensions methods.
  I have no compilation errors but when I call these methods have a sigabrt ... I do not find these methods! And 'I do not understand the strange and
  reason whatsoever.</p>