10

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.

4
  • I suggest you check its source, -1 sounds like it encountered an error and then intentionally returned an invalid result. Commented Jul 13, 2012 at 15:11
  • Why method selectedFeatureCount returns 0?
    – bossman
    Commented Jul 13, 2012 at 15:20
  • 2
    The obvious answer would be that the previous select call didn't select anything. Check your parameters. Commented Jul 13, 2012 at 15:23
  • In while I get one feature with polygon.
    – bossman
    Commented Jul 13, 2012 at 15:24

1 Answer 1

15

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.

0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.