[QGIS-Developer] How to create a simple processing script in QGIS 3.x, eg just a buffer

Andrew C andrew.cutts at gmail.com
Thu Aug 9 09:29:59 PDT 2018

Hi Anita,

Thanks very much for this. I am still lost though. If I replace the sink
and add your code I don't get an output in the dialog box - it needs to be
a parameter for that to happen right?

I found this
which lead me to this

Which is recommending "Best practice in 3.x Processing algorithms is to use
"feature sinks" instead of vector layer outputs"

Kind Regards

On Thu, Aug 9, 2018 at 2:23 PM Anita Graser <anitagraser at gmx.at> wrote:

> Hi Andrew,
> On Thu, Aug 9, 2018 at 2:57 PM Andrew C <andrew.cutts at gmail.com> wrote:
>> I am not clear on how QgsFeatureSinkis working, perhaps that is why I am
>> not getting the buffered layer? Normally in a script I could try printing
>> variables I cannot see where these are printed either when I tested.
> I think you'd need an output layer instead of a feature sink. Have a look
> at
> https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/qgis/PostGISExecuteAndLoadSQL.py
> self.addOutput(QgsProcessingOutputVectorLayer(
> self.OUTPUT,
> self.tr("Output layer"),
> QgsProcessing.TypeVectorAnyGeometry))
> Regards,
> Anita
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