QHash & dynamic_cast & memory leak

ask4

Hi
I have dynamic creation of widgets that I appending in QHash<int,QWidget*>
is this good valid approach?

bool CLASS::IsColorGraph(const QWidget * widget)
{
   return dynamic_cast<const ColorGraph*>(widget) != 0;
}
...
if(IsColorGraph(qhash[ID]){
  ColorGraph * b = dynamic_cast<ColorGraph *>(qhash[ID]);
  b->SetColor(QColor(Qt::red));
}

what will heppen with b pointer? is it memory leak?

[Added code tags ~kshegunov]

m.sue

Hi,

it's just a cast, so no leak.

-Michael.

kshegunov

@ask4 said in QHash & dynamic_cast & memory leak:

what will heppen with b pointer? is it memory leak?

The pointer will be freed when the stack unwinds, and as a consequence the pointer can't be leaked.

ColorGraph * b = dynamic_cast<ColorGraph *>(qhash[ID]);

As you already know that the type of that element is ColorGraph you can reinterpret_cast the pointer safely at that point, although the "gain" would be that you skip one lookup through the virtual table, which is practically nothing.

SGaist

Hi,

To add to my fellows, since you are dealing with QObject based classes, you should use qobject_cast.

ask4

thanks lads!