[QGIS-Developer] Custom python expression question
Matthias Kuhn 🌍
matthias at opengis.ch
Fri May 5 05:08:24 PDT 2017
Actually, there would also be the "context" which gives access to the
@layer variable (a QgsVectorLayer object) and other additional things.
It's just slightly more complex to set up because it's not proxied to
One will need to subclass QgsExpression.Function as done here:
And then register it manually.
I think we should also send this to the @qgsfunction in QGIS 3.
On 05/05/2017 12:42 PM, Nathan Woodrow wrote:
> Hey Andreas,
> Parent means the parent expression itself. So in a function, you can
> know what the whole expression is e.g it points to the instance of.
> You can't really know what the layer because expressions are not always
> layer bound and QgsFeatures don't hold a reference to the layer they are
> from. Best you can do at the moment I think is to pass the layer name
> or id into the custom expressions.
> - Nathan
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