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Is it possible to programmatically (in python) access the attribute info of the last added feature in QGIS 2.0 before edits are saved? I'm failing to find a way to get the ID and subsequently other attributes of my feature of interest (the one most recently added).

idx = layer.fieldNameIndex('myField')
myList = []
lastEdited = ID THAT I'D LIKE TO RETRIEVE
for feature in layer.getFeatures():
    if feature.id() == lastEdited:
        print feature.attributes()[idx]

From this I'd like to get 'myField' of my most recent addition.

UPDATE: Following lead of this thread, I was able to achieve my goals via the Python console, but am failing to get it to work for my plugin.

def updateTableWidget(self, fid):
    idx = layer.fieldNameIndex('myField')
    myList = []
    for feature in layer.getFeatures():
        if feature.id() == fid:
            myList.append(feature.attributes()[idx])

Via the python console, I was able to connect to my layer like so:

layer.featureAdded.connect(updateTableWidget)

After adding a QgsMessageLog to my function, the attributes were correctly identified. I now have a beginner python issue, however. Calling the function in my plugin as shown below gives me TypeError: updateTableWidget() takes exactly 2 arguments (1 given):

self.updateTableWidget()

The function was called from feature form python file.

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1 Answer 1

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To get the last added feature in QGIS I used the event AddedFeat:

self.connect(self.iface,SIGNAL("currentLayerChanged(QgsMapLayer *)") ,self.ChangedTarget) # in setup
self.connect(layer,SIGNAL("featureAdded(int)"),self.AddedFeat) # from the ChangedTarget

  def AddedFeat(self,id):
    # added feature by id.
    feat = QgsFeature()
    self.prelayer.featureAtId(id,feat)

This event has to be connected to the active layer so the connect/disconnect occurs in the ChangedTarget(self,layer): event.

This returns the feature as it is created, it wont have attributes yet but you can extract them based on a button click or other event qgsVectorLayer::committedAttributeValuesChange looks promising.

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5
  • How does ChangedTarget come into play exactly? Also, is prelayer different from layer in this case?
    – user25976
    Commented Jun 18, 2014 at 18:03
  • That's just me keeping track of which layer is what. In this case layer is the one switching to and prelayer is the layer switching from (or None), as the events need to be unhooked. ChangedTarget is fired when the user selects a layer from QgisInterface::currentLayerChanged.
    – Michael Stimson
    Commented Jun 18, 2014 at 21:32
  • I decided to programmatically activate the layer in my plugin, so I'm not sure this is applicable. I've edited my post after reading another thread, if you have any input as it's similar to your code.
    – user25976
    Commented Jun 18, 2014 at 22:01
  • Activate is activate, by user or program the event is still fired. It just needs to be wired before the activation.
    – Michael Stimson
    Commented Jun 18, 2014 at 22:35
  • Great, I see what you mean now. I connected to my layer in a run() method with the new connection style: self.layer.connect.featureAdded(updateTableWidget) and successfully connected. Also, I do seem to have the new attributes showing up in my message logs.
    – user25976
    Commented Jun 19, 2014 at 0:21

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