Custom QObject derived class as a parent in constructor definition

  • I have a class constructor like this(expecting MainWindow as a parent and deriving from QObject)

    class ActionManager : public QObject
        ActionManager(MainWindow *mainWindow, Settings *settings);
    ActionManager::ActionManager(MainWindow *mainWindow, Settings *settings) : QObject(mainWindow)

    This however, shows an error:

    error: C2664: 'QObject::QObject(const QObject &)': cannot convert argument 1 from 'MainWindow *' to 'QObject *'

    Should I reinterpret_cast this or it's a wrong way of doing this?

  • Moderators

    @enemyofthedawn It's the wrong way to do it. Typically your constructor would take either a QWidget * or a QObject * depending on your needs. Since QMainWindow is derived from both of those you can go either way (I would usually do QWidget for a widget since it's derived from QObject).

    So here is how it would normally be:

    // .h
    ActionManager(Settings *settings, QWidget *parent=nullptr);
    // .cpp
    ActionManager::ActionManager(Settings *settings, QWidget *parent) : QWidget(parent)

    Optionally if you need MainWindow* somewhere else in your ActionManager class (i.e. you are going to store it) then you can go ahead and use a qobject_cast<QWidget*> to pass it to QWidget's constructor.

  • @ambershark Thanks!

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