Is there any example about how to create a virtual field and subsequently change the attribute of a non-virtual field without wiping out the virtual field? Both are required to be done in the Python Console.
Answer
When you have a variable layer that is a reference to a vector layer you need
- to specify the field definition
- add the new field with an expression
-
field = QgsField( 'twoTimesA', QVariant.LongLong )
layer.addExpressionField( ' 2 * "A" ', field )
You can now modify an attribute and when you query the layer next time the virtual field will be updated.
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