Multiple inheritance of QObject

[Rua3n]

I'm trying to create a class in which all top-level widgets of my application could inherit from it, so I could define all Q_PROPERTY that I would like to expose in just this class instead of declaring it in each different class.

I'm getting compilation errors about ambiguous ~ because QMainWindow already inherits QObject.

What i can do in this case?

class WindowProperty : public QObject
{
    Q_OBJECT
	Q_PROPERTY(int test MEMBER test WRITE setTest)
public:
    int test = 0;
    void setTest(int xtest)
    {
        qDebug() << "xtest:" << xtest;
        qDebug() << "test:" << test;
    }
};


class MainWindow : public QMainWindow, public WindowProperty
{
    Q_OBJECT
public:
}

[Pl45m4]

@Rua3n

Why not include the properties instead of inherit from them?
"Making" QMainWindow "a property" (-> inheritance = "is a") doesn't make too much sense IMO

[Rua3n]

@Pl45m4 how to include Q_PROPERTIES?
What doesnt make sense? if you have 10 different classes that you want to share the same Q_PROPERTIEs, why keep track of defining all Q_PROPERTIES in each of these classes instead of just one?

[Pl45m4]

@Rua3n

If you really want to do this, you could try to make WindowProperty a Q_GADGET.
This doesn't allow signals and slots in there, since it's a light version of Q_OBJECT, but you can still use Q_PROPERTY from the MOC system.

[Rua3n]

@Pl45m4 I already had tried it, i get the same error using Q_GADGET

[ChrisW67]

It compiles just fine with Q_GADGET but it still will not do what you are expecting. The code generated by MOC is not heritable. (It's also in the WindowProperty private section where it would not be visible anyway. Changing that does not help.)

#include <QApplication>
#include <QMainWindow>
#include <QDebug>

class WindowProperty {  // not a QObject
    Q_GADGET
    Q_PROPERTY(int test MEMBER test WRITE setTest)
public:
    int test = 0;
    void setTest(int xtest)  {
        qDebug() << "xtest:" << xtest;
        qDebug() << "test:" << test;
    }
};

class MainWindow : public QMainWindow, public WindowProperty
{
    Q_OBJECT
public:
};

int main(int argc, char **argv) {
        QApplication app(argc, argv);
        MainWindow w;
        qDebug() << w.property("test");  // invalid variant, not 0
        w.setProperty("test", 42); // sets a property in w's QObject
        qDebug() << w.property("test"); // 42 , not 0
        return app.exec();
}
#include "main.moc"

[Rua3n]

@ChrisW67 im trying to inherit the Q_PROPERTIES from WindowProperty and use them in the MainWindow Isn't possible?