I have abstract class Interface with one pure virtual method

void Method(QMenuBar *menuBar, QWidget *parent = 0) const = 0;

I inherit this class with my plugin class. This method should add one QMenu widget to QMenuBar of app that loads plugin. App that is loadin my plugin inherits QMainWindow. I can load the plugin and call this method and it adds one menu item, but the problem is when I try to connect it with slot.

1. I have no idea where to put Q_OBJECT, in Interface or in Plugin or boath?
2. Does my class have to inherit QObject to be able to use signals and slots and wich one?