[Qgis-developer] Expression context and custom functions

[Nyall Dawson]

On 4 September 2015 at 01:12, Hugo Mercier <hugo.mercier at oslandia.com> wrote:
> Hi,
>
> I am using custom expressions functions for a plugin.
> Something like this :
>
> class MyFunction( QgsExpression.Function ):
>     def func( self, values, feature, parent ):
>         feature.geometry()
>         ...
>
> The problem is that "feature" is now a QgsExpressionContext(), not a
> QgsFeature anymore.
> I cannot find how to access the feature from the context. Did I miss
> something ?

The old API is fixed in 9133538 - sorry about that. I've renamed the
new method to funcV2 in the Python bindings.

> But even with the decorator, the problem is still the same: the
> 'feature' parameter of the custom function is not a QgsFeature anymore
> as it was on previous versions, but a QgsExpressionContext. And it seems
> there is no way to access the feature through the expression context.

> Looking at the source, the feature is stored in a variable called
> "_feature_", but trying to access this from the function returns None.

Should also be fixed with 9133538, but I'd appreciate confirmation.

Cheers,
Nyall


>
> Thanks
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