[PyQt] Decorated slot has no compatible signature

[Tony Arnold]

Florian,

On Mon, 2016-11-21 at 15:33 +0100, Florian Bruhin wrote:
> * Tony Arnold <tony.arnold at manchester.ac.uk> [2016-11-21 13:42:11
> +0000]:
> > On Sun, 2016-11-20 at 22:46 +0000, Tony Arnold wrote:
> > > Florian,
> > > 
> > > On Sun, 2016-11-20 at 21:19 +0100, Florian Bruhin wrote:
> > > > * Tony Arnold <tony.arnold at manchester.ac.uk> [2016-11-20
> > > > 19:16:01
> > > > +0000]:
> > > > > I'm using QNetworkManager to upload some files to a site. To
> > > > > see
> > > > > the
> > > > > progress I've defined a slot that gets connected to the
> > > > > uploadProgress
> > > > > signal.
> > > > > 
> > > > > The slot is defined:
> > > > > 
> > > > >     @pyqtSlot(int, int)
> > > > >     def updateDataTransferProgress(self, readBytes,
> > > > > totalBytes):
> > > > > 
> > > > > and is connected to a reply object thus:
> > > > > 
> > > > >  
> > > > > reply.uploadProgress.connect(self.updateDataTransferProgress)
> > > > > 
> > > > > However, this gives the error message:
> > > > > 
> > > > > TypeError
> > > > > "decorated slot has no signature compatible with
> > > > > uploadProgress(qint64,qint64)"
> > > > > 
> > > > > I'm running on Ubuntu 16.10 which has PyQt5.7. I believe slot
> > > > > verification has been tightened
> > > > > up in this version, but as far as I can see the above
> > > > > declaration
> > > > > is correct.
> > > > > 
> > > > > How can I fix this?
> > > > 
> > > > Use @pyqtSlot('qint64', 'qint64') instead.
> > > 
> > > Thanks. I tried this and I now get
> > > 
> > >     The debugged program raised the exception unhandled TypeError
> > >     "connect() failed between uploadProgress(qint64,qint64) and
> > >     updateDataTransferProgress()"
> > 
> > A bit more experimenting. I took Florian's code from https://riverb
> > ankc
> > omputing.com/pipermail/pyqt/2016-April/037370.html and modified it
> > to
> > put the slot inside a class. And it failed. It also fails changing
> > the
> > decoration to use 'qint64'. It fails with:
> > 
> > QObject::connect: Cannot connect
> > QNetworkReplyHttpImpl::downloadProgress(qint64,qint64) to
> > (null)::slot(qint64,qint64)
> > Traceback (most recent call last):
> >   File "slot_example.py", line 16, in <module>
> >     reply.downloadProgress.connect(obj.slot)
> > TypeError: connect() failed between downloadProgress(qint64,qint64)
> > and
> > slot()
> > 
> > 
> > Here is the version of the code:
> > 
> > from PyQt5.QtWidgets import QApplication
> > from PyQt5.QtCore import pyqtSlot, QUrl
> > from PyQt5.QtNetwork import QNetworkAccessManager, QNetworkRequest
> > 
> > class test():
> >     @pyqtSlot('qint64', 'qint64')
> >     def slot(self, num1, num2):
> >         pass
> > 
> > a = QApplication([])
> > 
> > obj=test()
> > 
> > nam = QNetworkAccessManager()
> > reply = nam.get(QNetworkRequest(QUrl('http://www.riverbankcomputing
> > .com
> > /')))
> > reply.downloadProgress.connect(obj.slot)
> > 
> > a.exec_()
> > 
> > Can others get this to work, or could this be to do with my system?
> > Ím
> > running on Ubuntu 16.10.
> 
> If your class isn't a QObject, @pyqtSlot won't work (as it registers
> the method as a "real" slot with Qt).
> 
> If you want to connect to a normal function, or a method of a
> non-QObject, then don't use @pyqtSlot (like Detlev suggested).

Thanks. Modified my class to inherit QObject and it all now works.

Fantastic!

Tony.
-- 
Tony Arnold MBCS, CITP | Senior IT Security Analyst | Directorate of IT Services | G64, Kilburn Building | The University of Manchester | Manchester M13 9PL | T: +44 161 275 6093 | M: +44 773 330 0039