Polymorphism fails with derived class of QGraphicsScene

LauraB

Hi,

I've derived QGraphicsScene into a class called DiagramScene like this :

DiagramScene.h

#include <QGraphicsScene>

class QGraphicsSceneMouseEvent;
class QMenu;
class QPointF;
class QGraphicsLineItem;
class QFont;
class QGraphicsTextItem;
class QColor;

class DiagramScene : public QGraphicsScene
{
    Q_OBJECT

public:
    explicit DiagramScene(QMenu *itemMenu, QObject *parent = 0);
  // ... The rest ain't relevant for the problem IMO
};

DiagramScene constructor:

DiagramScene::DiagramScene(QMenu *itemMenu, QObject *parent)
    : QGraphicsScene(parent)
{
    // irrelevant code, this was just to show you 
    // i called QGraphicsScene constructor at initialization
}

And then, the problem :

// I voluntarily simplified the code to illustrate the problem
DiagramScene myDiagramScene(....);
QGraphicsView myGraphicView(....);
myGraphicView->setScene(&myDiagramScene);
// At compilation I get this error :
// No matching function for call to QGraphicsView::setScene(DiagramScene*)
//  Candidate : QGraphicsView::setScene(QGraphicsScene*)

Please correct me if I'm wrong, which I certainly am, but I thought i would benefit from the polymorphism mechanism here.
This code works if I cast the pointer into a QGraphicsScene pointer, but I feel like this should work without the case.

Does someone have a clue?
Thanks a lot for reading !

Asperamanca

First thing I would check is your #includes. It sounds like the compiler at that point doesn't know the two classes are related - I often get this when a class is forward-declared, but I don't have the proper include where I want to convert types.