[Qgis-developer] Expression context and custom functions

[Hugo Mercier]

This is what the decorator does.
Except that I need it in a plugin: using the decorator rather than a
manual register/unregister make it crash on each reloading (I need to
reload it quickly during the development).

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.



On 04/09/2015 11:57, Barry Rowlingson wrote:
> Maybe I've misunderstood, but are you trying to define a new function
> to appear as an expression? Isn't that what the @qgsfunction decorator
> does? Do you need to define a new class for this?
> 
> http://nathanw.net/2015/01/19/function-editor-for-qgis-expressions/
> 
> On Thu, Sep 3, 2015 at 4:12 PM, 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 ?
>>
>> Thanks
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>