"not list it in Q_INTERFACES" Warning ?

deleted28

What is the problem here and how can I fix it ?
If more code necessary, please let me know, thank you.

/Projects/Cella_02/mycellitem.h:18: Warning: Class MyCellItem implements the interface QGraphicsItem but does not list it in Q_INTERFACES. qobject_cast to QGraphicsItem will not work!

#ifndef MYCELLITEM_H
#define MYCELLITEM_H

#include <QGraphicsItem>
#include <QPainter>

class MyCellItem : public QObject, public QGraphicsItem
{
    Q_OBJECT

public:
    MyCellItem();
    ~MyCellItem();

    QRectF boundingRect() const;

    void paint(QPainter* painter, const QStyleOptionGraphicsItem *, QWidget *);
};

#endif // MYCELLITEM_H

deleted28

OK, fixed it, but still do not understand, why this is necessary and what for.

class MyCellItem : public QObject, public QGraphicsItem
{
    Q_OBJECT
    Q_INTERFACES(QGraphicsItem)

public:
...

kshegunov

It's needed for multitude of things, one of which is to provide RTTI when such is disabled for the compiler. You should refer to the docs for a full explanation on the macro. Also you're better off deriving from QGraphicsObject instead of the way you're doing it now.

Kind regards.

deleted28

thanks for reply!

this way ?

class MyCellItem : public QGraphicsObject //, public QGraphicsItem
{
    Q_OBJECT
//    Q_INTERFACES(QGraphicsItem)


public:

ps. how to mark this thread as SOLVED ?

kshegunov

@wally123 said in "not list it in Q_INTERFACES" Warning ?:

this way ?

Yes. That's what I meant.