On Thu, 30 Aug 2018 at 00:01, C Hamilton <[email protected]> wrote:
>
> > 3) I see no reason to return a layer to QGIS if it has no data which is the
> > reason to check the feature count. In the processAlgorithm return statement
> > do I only return those layers that have data?
> >
> > return {
> > self.PrmPointOutputLayer: dest_id_pt,
> > self.PrmLineOutputLayer: dest_id_line,
> > self.PrmPolygonOutputLayer: dest_id_poly
> > }
>
> > You can omit these from the returned dictionary in this case - so if
> > you're recording the counts of features added to each sink, only add
> > entries to the results dictionary where the count is > 0.
>
> This almost did what was needed. It looks like calling
>
> (sinkPt, dest_id_pt) = self.parameterAsSink(parameters,
> self.PrmPointOutputLayer, context, fields,
> QgsWkbTypes.Point, epsg4326)
>
> is what determines what layers are added to QGIS and not the dictionary I
> return. I guess I'm going to need to call parameterAsSink the first time I
> have data to be added. This is going to make the code more messy, but I don't
> know another way to prevent empty layers from being added.
Sorry - I gave bad advice. Test if the parameter value *itself* is None. i.e.
if parameters[self.PrmPointOutputLayer] is None:
# output as been skipped
For safety you may want to check if the parameter is in included in
the dictionary too - otherwise callers who just "leave out" the
parameter will cause an exception. So:
if self.PrmPointOutputLayer not in parameters or
parameters[self.PrmPointOutputLayer] is None:
# output as been skipped
Nyall
>
> Calvin
>
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