Qt: Signals and slots Error: undefined reference to `vtable for

Question

Following example from this link: http://developer.kde.org/documentation/books/kde-2.0-development/ch03lev1sec3.html

#include 
#include 

        

Answer 1

This issue may be caused by some of the following reasons. I have stumbled on all of them from time to time.

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Your class header may be missing the Q_OBJECT macro. Add the macro to the header as already noted by other answers.

class MyWidg : public QWidget
{
    Q_OBJECT

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Your class header may not be parsed by the moc. Add the header file in the HEADERS definitions of your .pro (or .pri) project file.

HEADERS += file.h

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If none of the above is true, then you probably need to run qmake again to make sure moc parses the header again, just in case the Q_OBJECT macro was added in the header after the qmake was run. Just run qmake again.