No “committedFeaturesAdded” signal after dataProvider().addFeatures() - QGiS 2.14.8

Question

I'm working on plugin updating existing shapefile by adding new features to it. And I have a problem with signal that hasn't been emitted by QGIS, when I've added features to layer, using dataProvider().addFeatures(). I'm pretty sure that I have defined correctly connection signal and function, when it is emitted.

layer.committedFeaturesAdded.connect(self.onFeaturesAdded)

Becasue when I add feature using tool in QGIS from Digitizing Toolbar, it works fine and function is running.

The problem is when I add features manually - using python.

def selectFeatures(self,diviLayer, userLayer84):
        self.diviLayer=diviLayer
        self.userLayer84=userLayer84
        features=[]

        Processing.initialize()

        general.runalg('qgis:selectbylocation', self.userLayer84, self.diviLayer, u'intersects',0.000001,0)
        self.userLayer84.invertSelection()
        number=self.userLayer84.selectedFeatureCount()

        for feature in self.userLayer84.selectedFeatures():
            attributes=[feature['Lokaliz'],feature['Zadanie'],feature['Projekt'],feature['Wykonawca'],feature['X'],feature['Y'],feature['h'],feature['Azymut'],feature['Dokl'],feature['KmEt'],feature['Km2Et'],feature['Poloz'],feature['Domiar'],feature['Nr_dz'],feature['Obr'],feature['JE'],feature['Pow'],feature['Woj'],feature['Data'],feature['Czas'],feature['xtrPhtC'],feature['xtrComC'],feature['xtrAudC'],feature['xtrFilC'],feature['NazwaRap'],feature['Sciezka']]
            feat=QgsFeature()
            feat.setAttributes(attributes)
            feat.setGeometry(QgsGeometry.fromPoint(QgsPoint(float(feature['Y']),float(feature['X']))))
            features.append(feat)

        return [features,number]

    [features,number]=self.selectFeatures(self.diviLayer,self.userLayer84)

    self.diviLayer.startEditing()
    self.diviLayer.dataProvider().addFeatures(features)
    self.diviLayer.commitChanges()

It seems like the signal is not emitted? Has anyone of you had a similar problem? Or maybe you know, where I'm making mistake.

Answer 1

According to one of the QGIS developers (@MatthiasKuhn) in his website OPENGIS.ch, he suggests to completely avoid dataProvider() methods as he lists the following (emphasis mine):

• You cannot undo them easily
• They generate one request per call what may reduce performance
• They do not emit internal signals for map redraws and other refreshes of the user interface
• They do not take uncommitted changes into account so the python changes will get overwritten by the user when he commits the layer changes

I think the third bullet point states that the dataProvider() method will not emit any signals (I could be wrong).

---

In any case, it is suggested to instead use the with edit(layer): method. So you could try replacing your last three lines:

self.diviLayer.startEditing()
self.diviLayer.dataProvider().addFeatures(features)
self.diviLayer.commitChanges()

With this:

with edit(self.diviLayer):
    self.diviLayer.addFeatures(features)

Note that you may need to import the edit method into your plugin using:

from qgis.core import edit