[Qt-interest] destroyed() signal and sender()

[Thiago Macieira]

On Tuesday 02 December 2008 12:21:03 Anthony Serdyukov wrote:
> Some inherits QObject of course. But qobject_cast returns NULL, as
> dynamic_cast does too.
> Why so?

That happens because the destroyed() signal is emitted in QObject's 
destructor. As C++ goes, by the time the QObject destructor is run, the 
destructors for the more-specialised classes have already run and finished. 
That means your object is *really* a QObject at that point.

So qobject_cast is right when it returns 0: the cast did fail.

>Though static_cast works well, but it's not safe enough.

It's not a question of safety here: it's actually wrong. The object is no 
longer your type.

-- 
Thiago Macieira - thiago.macieira (AT) nokia.com
  Senior Software Engineer - Nokia, Qt Software
  Qt Software is hiring - ask me
      Sandakerveien 116, NO-0402 Oslo, Norway
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