Pure virtual class with singals and slots

[rubikon]

Hello.

I want to write a small tool and like to separate the business logic from the GUI so I can easily make and use different GUIs.

Therefore I've made a class which contains the business logic called AppCore. The GUI class(es) are called MainWindow.

My idea is to pass the constructor of the AppCore a reference to the GUI so the constructor of the AppCore can connect the AppCore singals to the GUI slots and vice versa.

But to make it flexible I don't want to have the actual GUI as type of the parameter but an Interface (pure virtual class) called IGui which the GUI inherits from.

class IGui
{
	public slots:
		virtual void slot() = 0;
 
	signals:
		virtual void signal() = 0;
};
 
class MainWindow : public QMainWindow, public IGui
{
	Q_OBJECT
 
	public:
		explicit MainWindow(QWidget *parent = 0);
		~MainWindow();
 
	private slots:
		void slot();
 
	signals:
		void signal();
 
	private:
		Ui::MainWindow *ui;
};
 
class AppCore : public QObject
{
	Q_OBJECT
 
	public:
		explicit AppCore(IGui *gui, QObject *parent = 0);
 
	signals:
		void doSlot();
 
	private slots:
		void onSingal();		
...
...
}
 
AppCore::AppCore(IGui *gui, QObject *parent) :
    QObject(parent)
{
	connect(gui, SIGNAL(signal()),
			this, SLOT(onSingal()));
 
	connect(this, SIGNAL(doSlot()),
			gui, SLOT(slot()));
}

class IGui
{
	public slots:
		virtual void slot() = 0;

	signals:
		virtual void signal() = 0;
};

class MainWindow : public QMainWindow, public IGui
{
	Q_OBJECT
		
	public:
		explicit MainWindow(QWidget *parent = 0);
		~MainWindow();
		
	private slots:
		void slot();

	signals:
		void signal();

	private:
		Ui::MainWindow *ui;
};

class AppCore : public QObject
{
	Q_OBJECT

	public:
		explicit AppCore(IGui *gui, QObject *parent = 0);

	signals:
		void doSlot();
		
	private slots:
		void onSingal();		
...
...
}

AppCore::AppCore(IGui *gui, QObject *parent) :
    QObject(parent)
{
	connect(gui, SIGNAL(signal()),
			this, SLOT(onSingal()));

	connect(this, SIGNAL(doSlot()),
			gui, SLOT(slot()));
}

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But when I try to compile I get errors:

AppCore.cpp: In constructor 'AppCore::AppCore(IGui*, QObject*)':
AppCore.cpp:9: error: no matching function for call to 'AppCore::connect(IGui*&, const char [10], AppCore* const, const char [12])'
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:204: note: candidates are: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:217: note: static bool QObject::connect(const QObject*, const QMetaMethod&, const QObject*, const QMetaMethod&, Qt::ConnectionType)
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:337: note: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
AppCore.cpp:12: error: no matching function for call to 'AppCore::connect(AppCore* const, const char [10], IGui*&, const char [8])'
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:204: note: candidates are: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:217: note: static bool QObject::connect(const QObject*, const QMetaMethod&, const QObject*, const QMetaMethod&, Qt::ConnectionType)
c:\QtSDK\Desktop\Qt\4.8.1\mingw\include\QtCore/qobject.h:337: note: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const

How do I have to do it right?

[Zlatomir]

One obvious problem is that IGui doesn't derive from QObject (or other QObject derived class), so it can't use signals and slots.

[rubikon]

If I let IGui derive from QObject I get this errors:

release\moc_MainWindow.cpp: In static member function 'static void MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)':
release\moc_MainWindow.cpp:52: error: 'QObject' is an ambiguous base of 'MainWindow'
release\moc_MainWindow.cpp: In member function 'virtual const QMetaObject* MainWindow::metaObject() const':
release\moc_MainWindow.cpp:78: error: 'QObject' is an ambiguous base of 'MainWindow'
release\moc_MainWindow.cpp:78: error: 'QObject' is an ambiguous base of 'MainWindow'
release\moc_MainWindow.cpp: In member function 'virtual int MainWindow::qt_metacall(QMetaObject::Call, int, void**)':
release\moc_MainWindow.cpp:98: error: 'QObject' is an ambiguous base of 'MainWindow'
release\moc_MainWindow.cpp: In member function 'virtual void MainWindow::signal()':
release\moc_MainWindow.cpp:107: error: 'QObject' is an ambiguous base of 'MainWindow'