On 20 June 2014 15:43, Martin Dobias <[email protected]> wrote: > > Actually the dot syntax would imply on the fly evaluation. When > parsing, it is not possible to decide what will be the content of an > object. > > This would be similar to python: the expression x.y means that in > object x it should look up "x" in the dictionary of attributes and > return its value.
I mean column names which are themselves the result of an evaluated expression. For eaxmple, if my table was something like: id, label_with, label1, label2 1000, 1, 'a', 'b' 1001, 2, 'a', 'b' I'd like to be able to label this with an expression like: attribute( feature, 'label' || "label_with"). If the column name was evaluated as a result of the 'label' || "label_with" expression, then the returned feature attribute value would be 'a' for feature 1000 and 'b' for feature 1001. (Sorry for the confusing example!). Could this be done using dot notation? > > I see. Another option could be to have a special column name that > would indicate that all columns are needed - this special name would > be understood by QgsFeatureRequest. That would keep the usage of > QgsExpression same as before, without having to discriminate between > the two cases... That sounds like it might be an easier approach, I'll give it a try! Cheers, Nyall _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
