Thanks! -----Original Message----- From: Stephen Kelly [mailto:stephen.ke...@kdab.com] Sent: 17 February 2014 10:06 To: Graham Labdon Cc: interest@qt-project.org Subject: Re: [Interest] QMetaType::metaObjectForType
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 > > > Q_DECLARE_METATYPE(Widget) > > 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 Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt 5.0. There's some background info here: http://steveire.wordpress.com/2011/03/16/implementing-qvariantqmetatype-features-with-template-tricks/ and the problems were solved and implemented in 5.0 http://www.kdab.com/kdab-contributions-to-qt-5-0-part-1/ 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). Thanks, -- Stephen Kelly <stephen.ke...@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 _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
