There's no real reason for CComListener to be a QObject if it is just an abstract interface. The public functions in the interface class can be treated as slots in the derived class For example, this seems to work:
Qt Code: 
  1. #include <QtGui>
  2. #include <QDebug>
  3.  
  4. // Class is abstract by virtue of having at least one pure virtual
  5. class IComLineObserver 
  6. {
  7. public:
  8.   explicit IComLineObserver() {}
  9.   virtual ~IComLineObserver() = 0;
  10.  
  11. // these can be slots in derived classes
  12.   virtual void OnTxLine( QString sLine ) {}
  13.   virtual void OnRxLine( QString sLine ) {}
  14.   virtual void OnRxChar( QString sLine ) {}
  15.   virtual void test() {}
  16. };
  17. IComLineObserver::~IComLineObserver() {};   // must have an implementation
  18.  
  19. class A: public QObject, public IComLineObserver 
  20. {
  21.     Q_OBJECT
  22. public:
  23.     A() { }
  24.     ~A() { }
  25. public slots:
  26.     void test() { qDebug() << "Test"; }
  27. };
  28.  
  29. int main(int argc, char *argv[])
  30. {
  31.     QApplication app(argc, argv);
  32.  
  33.     A a;
  34.     QTimer t;
  35.     QObject::connect(&t, SIGNAL(timeout()), &a, SLOT(test()));
  36.     t.start(1000);
  37.     return app.exec();
  38. }
  39. #include "main.moc"
To copy to clipboard, switch view to plain text mode