title: Doubled undefined reference to `vtable for Class'
body: <p>I'm planning to programm a Class for managing my Windows. It will depend on Signals and Slots. I checked a lot of Threads here about that topic but it didnt help me. Sp here is my Code.</p>
  
  <p>Header:</p>
  
  <pre><code>#ifndef WINDOWHANDLER_H
  #define WINDOWHANDLER_H
  
  #include &lt;QObject&gt;
  
  class WindowHandler : public QObject
  {
      Q_OBJECT
  
  public:
      WindowHandler();
  
  signals:
  
      void showFrmMain(bool);
      void showLogin(bool);
      void showRegister(bool);
      void showVerbindungsaufbau(bool);
  };
  
  
  #endif // WINDOWHANDLER_H
  </code></pre>
  
  <p>CPP:</p>
  
  <pre><code>#include "windowhandler.h"
  
  WindowHandler::WindowHandler()
  {
  
  }
  </code></pre>
  
  <p>I didnt wrote lot of Code here, but I stuck cause this problem very hard :/
  The complete Errormessage is: undefined reference to `vtable for WindowHandler'
  I got it two times. Both for the Constructor once in the .h and once in the .cpp.</p>
  
  <p>I hope You can help me and thanks!</p>