Hi Mariane,
I don't see the usage of Qt.UniqueConnection in your example.
This works for me:
def executeSel():
print('selection changed')
layer.selectionChanged.connect(executeSel, Qt.UniqueConnection)
layer.selectionChanged.connect(executeSel, Qt.UniqueConnection)
Traceback (most recent call last):
File "/usr/lib64/python3.5/code.py", line 91, in runcode
exec(code, self.locals)
File "<input>", line 1, in <module>
TypeError: connection is not unique
try:
layer.selectionChanged.connect(executeSel, Qt.UniqueConnection)
except TypeError:
pass # No reason to complain if it was already connected
Matthias
On 10/03/2017 01:48 PM, Tudorache, Marian wrote:
> Hi Mathias,
>
>
>
> Yeah, this is what I knew in theory. Unfortunately this is not the case.
>
> You can try in python console.
>
> Make sure you have a layer with some features.
>
> Define function executeAfterSelection where you do some dummy printing.
>
> Call three times layer.selectionChanged.connect(executeAfterSelection).
>
> Then try to select features in the layer.
>
> You will see the function executeAfterSelection is execute three times
> after each selection.
>
>
>
> I have done an workaround by introducing a flag variable which tells me
> if the myLayer.selectionChanged.connect(executeAfterSelection) statement
> was already called.
>
>
>
> Thanks,
>
> Marian
>
>
>
> *From:*Qgis-user [mailto:qgis-user-boun...@lists.osgeo.org] *On Behalf
> Of *Matthias Kuhn
> *Sent:* October-03-17 3:13 AM
> *To:* qgis-user@lists.osgeo.org
> *Subject:* Re: [Qgis-user] Check
if a selectionChanged signal is
> connected to any slot?
>
>
>
> Hi Marian,
>
> Just tell Qt that it shouldn't create the connection more than once
> using Qt::UniqueConnection.
>
> Cheers
>
> Matthias
>
>
>
> On 10/2/17 5:30 PM, Tudorache, Marian wrote:
>
>
>
> Hi everyone,
>
>
>
> I have connected the signal selectionChanged so some code, which is
> executed after features are selected.
>
>
>
> myLayer.selectionChanged.connect(self.executeAfterSelection)
>
>
>
> Then I have a method self. executeAfterSelection(self, featuresIds)
>
>
>
> The SIGNAl/SLOT tandem works but now I realized every time when I
> call *myLayer.selectionChanged.connect(self.executeAfterSelection)*
> It does not overwrite my previous call. It creates a second
> signa/slot tandem. During running the method executeAfterSelection
> is excuted twice, three times etc.
>
>
>
> How can I check if the SIGNAL selectionChanged is connected to the
> slot executeAfterSelection before I run
> myLayer.selectionChanged.connect(self.executeAfterSelection)?
>
>
>
> I tried this:
>
> receiversCount =
> QtCore.QObject.receivers(QtCore.SIGNAL(“selectionChanged()”)
>
> receiversCount =
> QtCore.QObject.receivers(QtCore.SIGNAL(“selectionChanged”)
>
> receiversCount =
> QtCore.QObject.receivers(QtCore.SIGNAL(“myLayer.selectionChanged()”)
>
> receiversCount =
> QtCore.QObject.receivers(QtCore.SIGNAL(“myLayer.selectionChanged”)
>
>
>
> Every time I get this error:
>
>
>
> QObject.receivers(SIGNAL()): first argument of unbound method must
> have type ‘QObject’).
>
>
>
>
>
> Thanks,
>
> Marian
>
>
>
>
>
>
>
>
>
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