Issues When Add the Q_OBJECT to My SubClass of QGraphicsRectItem

joeQ

like the head file, i had the subclass of QGraphicsRectItem.

#ifndef GRAPHICSRECTITEM_H
#define GRAPHICSRECTITEM_H

#include <QGraphicsRectItem>

class GraphicsRectItem : public QGraphicsRectItem
{
public:
    explicit GraphicsRectItem(const QRect &rect,QGraphicsItem *parent = Q_NULLPTR);
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

protected:
    /**...*/

private:

    /**...*/
private:

    /**...*/
};

#endif // GRAPHICSRECTITEM_H

Every thing was ok. Where was no Q_OBJECT

But, i want to use the signal and slot. so, i add the Q_OBJECT. like below.

class GraphicsRectItem : public QGraphicsRectItem
{
    Q_OBJECT
public:
    explicit GraphicsRectItem(const QRect &rect,QGraphicsItem *parent = Q_NULLPTR);
    /**...*/

Then, Has the some issues.

...error: 'staticMetaObject' is not a member of 'QGraphicsRectItem'...
...&QGraphicsRectItem::staticMetaObject, qt_meta_stringdata_GraphicsRectItem.data,...
...error: 'QScopedPointer<QObjectData> QObject::d_ptr' is protected QScopedPointer<QObjectData> d_ptr;
...error: within this context return QObject::d_ptr->metaObject ? QObject::d_ptr->dynamicMetaObject() : &staticMetaObject;
...

I just want to use the signal and slot. so Add the Q_OBJECT in my class. But There has some wrong!

I didn't understand Q_OBJECT well.

Thank u.

J.Hilk

@joeQ said in Issues When Add the Q_OBJECT to My SubClass:

Q_OBJECT

Hi, I would recomment you taking some time and reading throught the docu.

I'm not sure if QGraphicsRectItem actually subclasses of QObject but adding a #include <QObject> might help :)

dheerendra

QGraphicsRectItem is not from QObject. You can't do this. Why do you want add Q_OBJECT ?

joeQ

@J.Hilk

I add the #include<QObject>. it didn't work.

In the doc waht you said. I searched the QGraphicsRectItem or QGraphicsItem . and want to know that did them Inherited the QObject.
They didn't inherited QObject.

joeQ

@dheerendra

I want to use the signal and slot. I want to emit signal to scene(or to another rect item) when rect item size changed.

dheerendra

Then do something like this. It should work. Inherit from QObject.

class MyItem : public QObject,public QGraphicsRectItem
{
Q_OBJECT
public:
MyItem();
};

joeQ

@dheerendra

Yes, (0o0), it's ok! Thank u. Very much. Excellent.