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

[Andrew C]

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
https://gis.stackexchange.com/questions/282773/writing-a-python-processing-script-with-qgis-3-0
which lead me to this
https://github.com/qgis/QGIS/blob/master/doc/porting_processing.dox

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


Kind Regards
Andrew



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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20180809/7bacf404/attachment.html>