4

I'm using this code to get features from QgsVectorLayer

 QgsVectorDataProvider* provider=theVectorLayer->dataProvider();
            if(!provider)
            {
                return;
            }

            theVectorLayer->select(provider->attributeIndexes(),theVectorLayer->extent(),true,false);
    theVectorLayer->selectedFeatureCount();//here returns 0 but there is one polygon
    while(theVectorLayer->nextFeature(currentFeature))
            {
         ....//here Iget attributes and current geometry (one polygon)
            }

How do I get feature count?

Method featureCount() returns -1.

  • I suggest you check its source, -1 sounds like it encountered an error and then intentionally returned an invalid result. – lynxlynxlynx Jul 13 '12 at 15:11
  • Why method selectedFeatureCount returns 0? – bossman Jul 13 '12 at 15:20
  • 1
    The obvious answer would be that the previous select call didn't select anything. Check your parameters. – lynxlynxlynx Jul 13 '12 at 15:23
  • In while I get one feature with polygon. – bossman Jul 13 '12 at 15:24
9

When featureCount() returns -1 the only safe bet to get the feature count is to iterate over all feature and count them.

selectedFeatureCount() is the number of features that are selected on the layer (e.g. with setSelectedFeatures() or void select(QgsFeatureId featureId, bool emitSignal=true)), but has nothing to do with the select()/nextFeature() combo.

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