[Interest] QMetaType::metaObjectForType

Stephen Kelly stephen.kelly at kdab.com
Mon Feb 17 11:05:45 CET 2014

On Monday, February 17, 2014 09:47:20 you wrote:
> Hi
> Thanks for your quick reply.
> This does indeed work, but I would be grateful if you could explain why

> Remove this line.

You don't pass around copies of QObject derived types because it is not 
copyable. You pass around pointers instead. So, you don't want 'Widget' to be 
a metatype, you want 'Widget*' to be a metatype so that you can put a Widget* 
in a QVariant for example.

You can use 


but it is not needed as of Qt 5.0. There's some background info here:


and the problems were solved and implemented in 5.0


So, it's better to remove the Q_DECLARE_METATYPE that you don't need rather 
than add one that is wrong.

> > Class.cpp
> > const int WidgetTypeID = qRegisterMetaType<Widget>("Widget");
> Register the pointer. Don't specify the string:
>  qRegisterMetaType<Widget*>();

By using a string there, you run the risk of typos. The string is not needed 
and should not be used (even with Qt 4 code). 


Stephen Kelly <stephen.kelly at kdab.com> | Software Engineer
KDAB (Deutschland) GmbH & Co.KG, a KDAB Group Company
www.kdab.com || Germany +49-30-521325470 || Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-Independent Software Solutions
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