Cant access to superclass ...

[tonnot]

I have a G_item_base class, it has some properties I want to use at G_item_rect (a QGraphicsRect subclassed ) and others...
In example, I have this method:

A_GItem_base::A_GItem_base(qint64 internal_pointer, WW::Graph_type my_type) {
    w_internal_type= QGraphicsItem::UserType + my_type;                                }
 
void A_GItem_base::w_set_pen(QPen my_pen ) {
   ((QAbstractGraphicsShapeItem*)this->metaObject()->superClass())->setPen(my_pen);    }

A_GItem_base::A_GItem_base(qint64 internal_pointer, WW::Graph_type my_type) {
    w_internal_type= QGraphicsItem::UserType + my_type;                                }

void A_GItem_base::w_set_pen(QPen my_pen ) {
   ((QAbstractGraphicsShapeItem*)this->metaObject()->superClass())->setPen(my_pen);    }

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And the G_item_rect is declared as:

A_GItem_rect::A_GItem_rect (qint64 internal_pointer QGraphicsScene *scene, QGraphicsItem *parent ) : QGraphicsRectItem (parent,scene) ,  A_GItem_base(internal_pointer, WW::Graph_rectangle)

A_GItem_rect::A_GItem_rect (qint64 internal_pointer QGraphicsScene *scene, QGraphicsItem *parent ) : QGraphicsRectItem (parent,scene) ,  A_GItem_base(internal_pointer, WW::Graph_rectangle)

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Ok, I can't use Q_object macro. I have
" Class contains Q_OBJECT macro but does not inherit from QObject"

Any help ? Thanks

[Ginsengelf]

Hi, you don't need the Q_OBJECT macro in the class if it doesn't use signals and slots.

Ginsengelf

[tonnot]

Ok, ... What casting can i do .... I have tested all...

((QAbstractGraphicsShapeItem *) this)->setPen(my_pen);
QAbstractGraphicsShapeItem * r = reinterpret_cast<QAbstractGraphicsShapeItem*>(this ) ;

I have crash for both ...

Thanks.

[FelixB]

please post full class declaration

[tonnot]

Here you are :

class A_GItem_base {
   public:
     A_GItem_base(WW::Graph_type my_type);
     void w_set_pen(QPen my_pen );
};
 
A_GItem_base::A_GItem_base( WW::Graph_type my_type) { }
 
void A_GItem_base::w_set_pen(QPen my_pen ) {
  // or 
   QAbstractGraphicsShapeItem  * r = reinterpret_cast<QAbstractGraphicsShapeItem*>(this) ;
   r->setPen(my_pen);
 // or 
   ((QAbstractGraphicsShapeItem *) this)->setPen(my_pen);
 // both crashes 
}
 
class A_GItem_rect : public QGraphicsRectItem , public  A_GItem_base {
public:
    A_GItem_rect(QGraphicsScene *scene = 0, QGraphicsItem *parent = 0 );
    void w_set_rect( QRect rectf) ;
};
 
A_GItem_rect::A_GItem_rect (QGraphicsScene *scene, QGraphicsItem *parent ) : QGraphicsRectItem (parent,scene) ,  A_GItem_base(WW::Graph_rectangle) { }
void A_GItem_rect::w_set_rect( QRect rectf) {   this->setRect(rectf); }

class A_GItem_base {
   public:
     A_GItem_base(WW::Graph_type my_type);
     void w_set_pen(QPen my_pen );
};

A_GItem_base::A_GItem_base( WW::Graph_type my_type) { }

void A_GItem_base::w_set_pen(QPen my_pen ) {
  // or 
   QAbstractGraphicsShapeItem  * r = reinterpret_cast<QAbstractGraphicsShapeItem*>(this) ;
   r->setPen(my_pen);
 // or 
   ((QAbstractGraphicsShapeItem *) this)->setPen(my_pen);
 // both crashes 
}

class A_GItem_rect : public QGraphicsRectItem , public  A_GItem_base {
public:
    A_GItem_rect(QGraphicsScene *scene = 0, QGraphicsItem *parent = 0 );
    void w_set_rect( QRect rectf) ;
};

A_GItem_rect::A_GItem_rect (QGraphicsScene *scene, QGraphicsItem *parent ) : QGraphicsRectItem (parent,scene) ,  A_GItem_base(WW::Graph_rectangle) { }
void A_GItem_rect::w_set_rect( QRect rectf) {   this->setRect(rectf); }

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I have :
A_GItem_rect * my_rect = new A_GItem_rect(this->scene()) ;
my_rect->w_set_pen(a_pen);


I'm trying to do this strange casting because I dont know how to access to the superclass of A_GItem_Base ...


Thanks

[Ginsengelf]

Hi, do you really need the w_set_pen() method in A_GItem_base? Because if you remove it and call setPen() on your instance of A_GItem_Rect, the method of the base class should be called.

Ginsengelf

[ChrisW67]

Ok, I can't use Q_object macro. I have
" Class contains Q_OBJECT macro but does not inherit from QObject"

Any help ? Thanks

The error message tells you exactly what the problem is. The Q_OBJECT macro installs some support code for the Qt meta-object system. A_GItem_base is not derived from QObject and therefore does not support anything that needs the Qt meta-object extensions... including signals and slots.

[tonnot]

Ginsengelf:
Yes I need to have control on this. (I know I can use setpen()... ) .

Chris: Yes, I understand. I wanted to use metaobject to discover the superclass.

By now, I have w_set_pen for every class....

Class A
Class B : extending A and Z
Class C : extending A and Z
...
Class M : extending A and Z

I need to set or use a Z property/method from A. And I need to check it and other things.
So.... How can I, inside A , have access to Z inherited methods of my superclass (B, C, or any ).
Thanks for your patience

[stampede]

Why not trying with composition instead of inheritance:

class A_GItem_base {
   public:
     A_GItem_base(WW::Graph_type my_type) : _itemPtr(NULL){
     }
     void w_set_pen(QPen my_pen ){
         if( _itemPtr ) _itemPtr->setPen(my_pen);
     }
    // here you can implement all methods that will use the QGraphicsItem class methods
protected:
     QGraphicsItem * _itemPtr;
};
 
class A_GItem_rect : public  A_GItem_base {
public:
    A_GItem_rect(QGraphicsScene *scene = 0, QGraphicsItem *parent = 0 ) : A_GItem_base(WW::Graph_rectangle){
        this->_itemPtr = new QGraphicsRectItem(parent,scene);
    }
    void w_set_rect( QRect rectf){
        if( QGraphicsRectItem * r = dynamic_cast<QGraphicsRectItem*>(_itemPtr) )
            r->setRect(rectf);
    }
};

class A_GItem_base {
   public:
     A_GItem_base(WW::Graph_type my_type) : _itemPtr(NULL){
     }
     void w_set_pen(QPen my_pen ){
         if( _itemPtr ) _itemPtr->setPen(my_pen);
     }
    // here you can implement all methods that will use the QGraphicsItem class methods
protected:
     QGraphicsItem * _itemPtr;
};
 
class A_GItem_rect : public  A_GItem_base {
public:
    A_GItem_rect(QGraphicsScene *scene = 0, QGraphicsItem *parent = 0 ) : A_GItem_base(WW::Graph_rectangle){
        this->_itemPtr = new QGraphicsRectItem(parent,scene);
    }
    void w_set_rect( QRect rectf){
        if( QGraphicsRectItem * r = dynamic_cast<QGraphicsRectItem*>(_itemPtr) )
            r->setRect(rectf);
    }
};

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If somehow in class "base" you need to know some data or methods specific to A_GItem_rect, then you should reconsider your design, and use virtual methods properly.

[tonnot]

Ok, this point of view is really what I need.
Thank you very much.