Inheritance and QpaintEvent

[djoul]

Hi, I'm a Qt beginner.
I've got problems dealing with inheritance and qwidget :
I've got a class that does all the painting stuff on a widget : class Current.
I've got a class Mother, and a class Son and a class Daugther that inherit from her.

In my class Current, I've got a static list of Mother elements(that can either be Son or Daughter) : static QList<Mother*> mother_list.
I do some : mother_list.append(new Son(attributes));

What I want is : for all the elements of my mother_list, I throw a method draw (virtual) so that the Son and Daughter can do some painting stuff themselves. So they have to have some link with the widget created in the Current Class.

The problem I have is that when I call "draw", the method is never called in the class Son or Daughter.
I think I've done big mistakes with passing the arguments, with the inheritance. Here is a part of the .h :

class Mother: public QWidget
{
    public :
        Mother(QWidget *parent, const Obj1&o1, const Obj2&ob2);
        virtual ~Mother();
        virtual void draw()=0;
                                 ......

class Mother: public QWidget
{
    public :
        Mother(QWidget *parent, const Obj1&o1, const Obj2&ob2);
        virtual ~Mother();
        virtual void draw()=0;
                                 ......

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class Son: public Mother
{
 
 
public : 
    Son(QWidget *parent, const Obj1&ob1, const Obj2&ob1, const Obj3&Ob3, const Obj4&Ob4);
    ~Son();
    void draw();
                  ...
protected :
    void paintEvent(QPaintEvent *);

class Son: public Mother
{

    
public : 
    Son(QWidget *parent, const Obj1&ob1, const Obj2&ob1, const Obj3&Ob3, const Obj4&Ob4);
    ~Son();
    void draw();
                  ...
protected :
    void paintEvent(QPaintEvent *);

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Daugher is the same as son.

So when in my current class I call mother_list.at(i)->draw();
Nothing is called.
Can you help me please !!!

[munna]

Just call mother_list.at(i)->repaint() which will automatically call the paintEvent().

[djoul]

I tried it, but I've got the same result : the paintEvent is not called
It even doesn't call my class Mother paintEvent if I implement him !!!

[fullmetalcoder]

try declaring the destructor, the paintEvent and the draw method as "virtual"...

[djoul]

You mean I call virtual even my Son and Daughter methods ? I thought it was just for the Mother class !

[fullmetalcoder]

You mean I call virtual even my Son and Daughter methods ? I thought it was just for the Mother class !

At this point thoughtq won't make your code work... Try it and see...

[djoul]

It still doesn t work ...

[fullmetalcoder]

class Mother : public QWidget
{
    Q_OBJECT
 
    public:
        Mother();
        virtual ~Mother();
 
    protected:
        virtual paintEvent(QPaintEvent *e) {}
};
 
class Son : public Mother
{
    Q_OBJECT
 
    public:
        Son();
        virtual ~Son();
 
    protected:
        virtual paintEvent(QPaintEvent *e) { qDebug("Son : paintEvent"); }
}
 
// somewhere in the code :
Son *pSon = ...
pSon->update();

class Mother : public QWidget
{
    Q_OBJECT
 
    public:
        Mother();
        virtual ~Mother();
 
    protected:
        virtual paintEvent(QPaintEvent *e) {}
};
 
class Son : public Mother
{
    Q_OBJECT
 
    public:
        Son();
        virtual ~Son();
 
    protected:
        virtual paintEvent(QPaintEvent *e) { qDebug("Son : paintEvent"); }
}
 
// somewhere in the code :
Son *pSon = ...
pSon->update();

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What does such a code outputs?

[djoul]

In my code, I added the Q_OBJECT that I had forgotten, I tried what you wrote and this is weird, the Son's paintEvent method is never called !!!
I even tried adding a public method draw in my Son class,with just update() in its body.
And then trying son->draw() but nothing happens.
And, if I put just virtual to the Son and Mother paintEvent method I get the error :

V4 error LNK2001: symbole externe non rÚsolu "protected: virtual void __thiscall Mother:aintEvent(class QPaintEvent *)" (?paintEvent@Weather@@MAEXPAVQPaintEvent@@@Z)

I must add =0 to the virtual paintEvent in the Mother class,
or delete the virtual in virtual paintEvent in my Son class.

For me, the natural code would be in the Mother class : virtual void paintEvent(...)=0 and the destructor virtual.
And in My son class : void paintEvent(...){.........} with the destructor not virtual.
(But I almost tried all the possible configurations)

[jacek]

And then trying son->draw() but nothing happens.

What should happen? How did you try to invoke it? How did you create that object?
Could you prepare minimal compilable example that reproduces the problem?

[djoul]

What should happen? How did you try to invoke it? How did you create that object?
Could you prepare minimal compilable example that reproduces the problem?

In my Son paintEvent I create a file and write some stuff in it and I try to draw some text on my widget to be sure the function is called but the file is never created, so my paintEvent method is never called.
In anoter class I just do Son *son = new Son(...);
son->draw() and as I specified draw as public it should work.

I'll try to prepare a minimal example