[Qt-interest] Comparing two QMetaObjects

[Oliver.Knoll at comit.ch]

On 2011-02-07 Gustavo Gustavo de Sá Carvalho Honorato wrote:

> ...
> Suppose I have a object 'a' of a class 'A'. It is guaranteed that
> a->metaObject() will aways return a pointer to A::staticMetaObject?
> Then I can aways compare using:
> 
> a->metaObject() != &A::staticMetaObject ?

I am not sure whether a->metaObject will return a pointer to the A::staticMetaObject instance! In fact I doubt it very much, since I think every instance of QObject as its OWN instance of meta object (for the concrete signal/slot connections).

What is it actually you want to achieve again? Do you want to know whether a given instance is of a specific class? Usually that is done with http://doc.qt.nokia.com/4.7/qobject.html#inherits (which makes use of the meta objects), as in:

  if (a->inherits(A::staticMetaObject().className()) {...}

(Note: this approach also works if you rename the class A during some refactoring)

Cheers, Oliver
--
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22