What's the difference between qt cast from normal C++ cast

I wonder what's the difference between qt cast like qgraphicsitem_cast, qobject_cast, qvariant_cast from normal C++ cast like "(QGraphicsRectItem *)item"?
Thanks in advance.

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Originally Posted by Seishin

I wonder what's the difference between qt cast like qgraphicsitem_cast, qobject_cast, qvariant_cast from normal C++ cast like "(QGraphicsRectItem *)item"?
Thanks in advance.

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"(QGraphicsRectItem*)item" is not a "normal C++ cast", it's an ugly C cast. In C++ it should be static_cast<QGraphicsRectItem*>(item) or reinterpret_cast<QGraphicsRectItem*>(item).

Anyway... different casts use different techniques for checking if the cast is valid or not. qobject_cast uses information from QMetaObject, qgraphicsitem_cast uses QGraphicsItem::type(), qvariant_cast uses QVariant::type(). C++ has also another important cast -- dynamic_cast that uses RTTI information provided by the compiler.

Thanks for the information. Just restudied basic c++ casting. This is really helpful.