Creating QgsFeatureSink without using parameterAsSink

Question

I know I can create a (QgsFeatureSink, string) tuple by calling

(sink, dest_id) = self.parameterAsSink(...)

However that requires me to pass an output layer as a parameter:

self.addParameter(
 QgsProcessingParameterFeatureSink(
 self.OUTPUT,
 self.tr('Some output layer'),
 QgsProcessing.TypeVectorPolygon
 )
)

But in a lot of cases, I really don't want this feature layer as an output. I might use it only for temporary processing. For instance I might generate a number of features and then rasterize them and only present the rasterized result to the user.

How can I create a similar sink from code that only resides in memory during the processing of the algorithm, and is not presented to the user?

• Ben W: Maybe QgsProcessingUtils.createFeatureSink() can help you. Link to docs: qgis.org/api/… And some examples: github.com/qgis/QGIS/search?q=createFeatureSink

Answer 1

As per Ben's suggestion, you can use createFeatureSink as a drop-in replacement. The only thing to be aware of, is to use memory: as destination URI. Something that seems to be missing from the official documentation

(sink, dest_id) = QgsProcessingUtils.createFeatureSink(
 'memory:',
 context,
 self.source.fields(),
 self.source.wkbType(),
 self.source.sourceCrs()
)