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List:       pykde
Subject:    Re: [PyQt] QCoreApplication.aboutToQuit not a signal...
From:       Phil Thompson <phil () riverbankcomputing ! com>
Date:       2016-12-16 0:42:02
Message-ID: F138D2F1-BA85-4FB9-A657-494475E7A8FC () riverbankcomputing ! com
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On 15 Dec 2016, at 11:38 pm, David Cortesi <davecortesi@gmail.com> wrote:
> 
> Per the Qt docs [1], aboutToQuit is a signal emitted by QCoreApplication.
> 
> However when I attempt this in a QWidget-based class,
> 
> class Mine( QWidget ) :
> def __init__( self, parent ) :
> super().__init__( Parent )
> QCoreApplication.aboutToQuit.connect( self.quittin )

How does it know which QCoreApplication instance is emitting the signal?

> this produces an error, 'PyQt5.QtCore.pyqtSignal' object has no attribute 'connect' -- which \
> tells me that QCoreApplication is not a signal but a PyQt signal factory (?) so, following \
> the directions in [2]: 
> class Mine( QWidget ) :
> about_to_quit = QCoreApplication.aboutToQuit()
> def __init__( self, parent ) :
> super().__init__( Parent )
> about_to_quit.connect( self.quittin )
> 
> Nope, that gets the error "native Qt signal is not callable" -- so it isn't a pyqtSignal \
> after all, it's a real signal. 
> So then accidentally I entered this:
> 
> class Mine( QWidget ) :
> about_to_quit = QCoreApplication.aboutToQuit # <-- no parens!
> def __init__( self, parent ) :
> super().__init__( Parent )
> about_to_quit.connect( self.quittin )
> 
> That executes without error! (So when it is assigned to a class variable, \
> QCoreApplication.aboutToQuit somehow acquires a .connect attribute?) 
> But however alas -- no signal is delivered, or at any rate self.quittin() is never entered.
> 
> So I could use some enlightenment here...

connect() is a method of bound signals, so...

QCoreApplication.instance().aboutToQuit.connect(self.quittin)

Phil
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