How to get sender widget with a signal/slot mechanism?

Question

It's possible to bind more than one signal to one slot (isn't?). So, is there a way to understand which widget sends the signal? I'm looking for something like sender argument of events in .NET

score 144 · Answer 1 · edited Jan 05 '16 at 15:07

144

Use QObject::sender() in the slot, like in the following Example:

void MainWindow::someSetupFunction( void )
{
   ...
   connect( _foobarButton, SIGNAL(clicked()), this, SLOT(buttonPressedSlot()) );
}

void MainWindow::buttonPressedSlot()
{
   // e.g. check with member variable _foobarButton
   QObject* obj = sender();
   if( obj == _foobarButton )
   { 
      ...
   }

   // e.g. casting to the class you know its connected with
   QPushButton* button = qobject_cast<QPushButton*>(sender());
   if( button != NULL ) 
   { 
      ...
   }

}

edited Jan 05 '16 at 15:07

mitjap

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answered Sep 13 '13 at 11:47

Teh Suu

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1

isn't qobject_cast better than plain dynamic_cast? – elephant Sep 24 '15 at 07:07
1

@elephant Yes, as desribed on http://doc.qt.io/qt-4.8/metaobjects.html . This should be improved in the answer. – Johannes Dec 30 '15 at 20:56

score 94 · Accepted Answer · edited Dec 13 '17 at 12:50

94

QObject::sender() will do the job.

edited Dec 13 '17 at 12:50

Fredrick Gauss

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answered Oct 28 '10 at 20:55

Idan K

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Arnold Spence · Answer 3 · 2015-06-03T00:04:37.803

8

Yes, you can connect multiple signals to one slot. In this case you would use QSignalMapper to differentiate the sources of the signals. This solution is limited to parameterless signals. You can see an example here.

edited Jun 03 '15 at 00:04

answered Oct 28 '10 at 20:46

Arnold Spence

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How to get sender widget with a signal/slot mechanism?

3 Answers3

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