[Qgis-developer] virtual fields

Denis Rouzaud denis.rouzaud at gmail.com
Mon Mar 3 08:52:59 PST 2014


First, nice to hear that this feature seems to be awaited!

> I have thought about this functionality before and I think it should
> be relatively easy to add this functionality. The
> QgsVectorLayerFeatureIterator could simply compute the values of the
> virtual fields according to their definition in QgsVectorLayer. It
> should automatically work lazily - if the field is not requested, it
> would not be evaluated.
nice to hear!
>> Then, it should be made possible to integrate the joined fields in qgis
>> expressions without adding them to the current attributes (as it is now).
>> One way to to it could be a function: joinField( joinName, joinedFieldName)
>> Hence, the user would be allowed to choose which joined fields he really
>> wants to be accessible in the layer.
> Do we actually need such functionality? Wouldn't it be enough to hide
> the attributes you don't want?
I thought it might allow to clean the code related to joined fields by 
moving it to QgsExpression evaluation.
I don't know really well how it's implemented, but I just notice that 
there has been many bugs on a long period.
If you think it should be kept separated, ok for me!



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