Class Promotion ?

[A Former User]

You mean events that have been sent to A but haven't been "delivered" to it yet?

[Walux]

Yes , how can i assign all of them to the new class B ?

[A Former User]

Call QCoreApplication::processEvents before destroying A.

[Walux]

@mrjj

Maybe i should do this instead :

I start by creating a class B that uses the paintEvent of class A , then when i reach the certain state , it calls the paintEvent of class B .

I have no problem doing it now , since the difference is only in the painting , but later when the new classes have new variables , that'll be a problem .

[Walux]

@Wieland

Maybe a small piece of code will help me understand better , and thank you :)

[Walux]

I'm sure the answer i'm looking for lays somewhere between :

• dynamic_cast
• virtual
• operator=

[mrjj]

I dont understand why it ever need to change "type".
I think you need to rethink the design.
Normally u use base class pointers and childs for polymorph operations but
i cannot understand your use case.

Its like circle that must sudden draw as a rect?

[Walux]

@mrjj
@Wieland

I'll try to minimize the code , to help clarify my situation :

Class myScene : public QGraphicsScene
{
//...
void MousePressEvent(QGraphicsSceneMouseEvent *event)
//...
private:
A *a;
//...
}

"myScene.cpp"

myScene::myScene 
{
a = new A;
}

void  myScene::MousePressEvent(QGraphicsSceneMouseEvent *event)
{
a->doesSmth();
if(a->reachesSomePoint())
a = new B;   // Compiles good but i lose the events and the whole paint of a;
}

Class A : public QObject , public QGraphicsItem
{
//...
    A();
    QRectF boundingRect() const Q_DECL_OVERRIDE;
    QPainterPath shape() const Q_DECL_OVERRIDE;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
               QWidget *widget) Q_DECL_OVERRIDE; // This is the first painting

    
//...
      protected:
qreal myValue1;
int myValue2;
//...
}

Class B : public Class A
{
        void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
               QWidget *widget) Q_DECL_OVERRIDE; // This is the second painting
//Future Variables
       private:
qreal futureValue1;
//...
}

[mrjj]

hi
You only need to go from base to child?
You can use a cast for that.
http://www.bogotobogo.com/cplusplus/upcasting_downcasting.php

and you dont lose A paint as you are free to call the A::paintEvent from
B::paintEvent.

[Walux]

@mrjj

Thanks for your help , glad you stayed with me till the bottom ;)
Imma read the content of your link :)

[Walux]

Hmm , very informative , and i can get the slicing problem now :)
But , it won't be of any harm till late versions of my program :)
Thank you very much :D

Topic->setAsSloved(true);

[mrjj]

@Walux
Np.
Its not always you run into slicing but its good to know it can happen.