Error when using Qt connect with interface and new synthax - c++

Question

First let me quickly introduce myself.
My name is Jonathan and I'm a video game technical artist and developer from Belgium.
I work mainly with C# or other script languages like Max Script, Python or Mel, and I begin to code in C++. I already did some little software in Visual Studio with WinForm and WPF.
StackOverflow was/and will be always an incredible resource for me.
I register because I moved further in my C++/Qt learning and I am now stuck with a Qt design and code problem.
I used the MVP pattern by the past for WinForm applications, and try to do the same with Qt. So I investigate and found the interface with Q_DECLARE_INTERFACE(MyInterfaceClass, "interfaceNameString") and QT_INTERFACES in the class that will implement the interface.
But I have a problem to connect the signal from the interface to a slot from and in my presenter.
error: no matching function for call to 'Presenter::connect(QObject*&, void (IView_Creator::)(), Presenter, void (Presenter::*)())'
QObject::connect(object,&IView_Creator::CreatorTest, this, &Presenter::Create);
error: no type named 'type' in 'struct std::enable_if'
The interface : (iview_creator.h)
#ifndef IVIEW_CREATOR_H
#define IVIEW_CREATOR_H
#include <QtPlugin>
class IView_Creator
{
public:
virtual ~IView_Creator(){}
virtual void WriteSomething() = 0;
signals:
virtual void CreatorTest() = 0;
};
Q_DECLARE_INTERFACE(IView_Creator, "interface")
#endif // IVIEW_CREATOR_H
The main class : (mainWindow.h)
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "iview_creator.h"
namespace Ui
{
class MainWindow;
}
class MainWindow : public QMainWindow ,public IView_Creator
{
Q_OBJECT
Q_INTERFACES(IView_Creator)
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
// IView_Creator interface
signals:
void CreatorTest();
};
#endif // MAINWINDOW_H
The presenter class : (presenter_creator.h)
#ifndef PRESENTER_H
#define PRESENTER_H
#include <QObject>
#include "mainwindow.h"
class Presenter : private QObject
{
Q_OBJECT
public:
Presenter(const MainWindow* mw);
private:
void Initialize(IView_Creator* mw);
private slots:
void Create();
};
#endif // PRESENTER_H
The implementation of the presenter :
#include "presenter_creator.h"
Presenter::Presenter(const MainWindow *mw)
{
IView_Creator *i = qobject_cast<IView_Creator*>(mw);
if(i != NULL)
Initialize(i);
}
void Presenter::Initialize(IView_Creator *mw)
{
auto object = dynamic_cast<QObject*>(mw);
Q_ASSERT(object);
QObject::connect(object, SIGNAL(CreatorTest()), this, SLOT(Create()));
//QObject::connect(object,QOverload<QObject*>::of(&IView_Creator::CreatorTest), this, &Presenter::Create);
QObject::connect(object,&IView_Creator::CreatorTest, this, &Presenter::Create);
mw->WriteSomething();
}
void Presenter::Create()
{
printf("Create");
}
The main class :
#include "mainwindow.h"
#include "presenter_creator.h"
#include <QApplication>
static Presenter* pt = NULL;
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
MainWindow *mw = &w;
pt = new Presenter(mw);
w.show();
return a.exec();
}
The problem appear when I try to use the new synthax system of the connect function. I seems to work with the old SIGNAL SLOT string system.
I already try everything I found on the net but with no luck.
Maybe someone with more C++ and Qt knowledge could know how to solve this problem.

Answer 1

This can't work with the new signal-slot syntax since QObject doesn't inherit from IView_Creator.
The fundamental difference between the old and the new syntax is that with the old syntax QObject::connect checks at runtime whether the signal and the slot of the connection actually exist, while this check is performed at compile time with the new syntax.
However, after your cast of mw to QObject* the information that object actually also is an instance of IView_Creator is lost to the implementation of QObject::connect. All it knows is that &IView_Creator::CreatorTest needs an object of a subtype of IView_Creator and that not every QObject (that's all it knows about object) is also an IView_Creator, so it can't guarantee that this connection can always be created. Therefore it fails to compile.