title: Qt5: error: ‘qt_metacall’ is not a member of
body: <p>I try to become more familiar with singnals and slots with Qt.
  I want to emit a signal in one class and want to handle it at one other.
  Here my example code:</p>
  
  <p><em>main.c</em></p>
  
  <pre><code>#include "mainwindow.h"
  #include &lt;QApplication&gt;
  
  int main(int argc, char *argv[])
  {
      QApplication a(argc, argv);
      MainWindow w;
      w.show();
  
      return a.exec();
  }
  </code></pre>
  
  <p><em>mainwindow.h</em></p>
  
  <pre><code>#ifndef MAINWINDOW_H
  #define MAINWINDOW_H
  
  #include &lt;QMainWindow&gt;
  
  class Emiter
  {
  
  signals:
      void anSignal ();
  };
  
  class MainWindow : public QMainWindow
  {
      Q_OBJECT
  
  private slots:
      void handleEmitter ();
  
  public:
      MainWindow(QWidget *parent = 0);
  };
  
  #endif // MAINWINDOW_H
  </code></pre>
  
  <p><em>mainwindow.cpp</em></p>
  
  <pre><code>#include "mainwindow.h"
  
  MainWindow::MainWindow(QWidget *parent)
     : QMainWindow(parent)
  {
      auto emiter = new Emiter();
  
      connect( emiter,
               &amp;Emiter::anSignal,
               this,
               &amp;MainWindow::handleEmitter );
  }
  
  void
  MainWindow::handleEmitter()
  {
  }
  </code></pre>
  
  <p>Then I get this error:</p>
  
  <pre><code>error: ‘qt_metacall’ is not a member of ‘Emiter’          enum { Value =  sizeof(test(&amp;Object::qt_metacall)) == sizeof(int) };
  </code></pre>
  
  <p>What does this mean?</p>