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https://issues.apache.org/jira/browse/BEAM-5524?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Luke Cwik reassigned BEAM-5524:
-------------------------------
Assignee: Luke Cwik
> PTransform style guide error
> ----------------------------
>
> Key: BEAM-5524
> URL: https://issues.apache.org/jira/browse/BEAM-5524
> Project: Beam
> Issue Type: Bug
> Components: website
> Affects Versions: 2.6.0
> Reporter: Simon Waddington
> Assignee: Luke Cwik
> Priority: Minor
> Time Spent: 20m
> Remaining Estimate: 0h
>
> On the page [https://beam.apache.org/contribute/ptransform-style-guide/] the
> example for Transforms with multiple output collections has a method
> {code:java}
> PCollectionTuple apply(... input) {
> ...
> PCollection<Moo> moo = ...;
> PCollection<Blah> blah = ...;
> return PCollectionTuple.of(mooTag, moo)
> .and(blahTag, blah);
> }{code}
> I'm no expert - just trying to understand that use case - but it seems to me
> it should be overriding the method {{expand}} of {{PTransform}} as in this
> [ParDoTest.java|https://github.com/apache/beam/blob/279a05604b83a54e8e5a79e13d8761f94841f326/sdks/java/core/src/test/java/org/apache/beam/sdk/transforms/ParDoTest.java#L301]
> code which does a similar thing.
> {code:java}
> static class MultiFilter
> extends PTransform<PCollection<Integer>, PCollectionTuple> {
> private static final TupleTag<Integer> BY2 = new TupleTag<Integer>("by2"){};
> private static final TupleTag<Integer> BY3 = new TupleTag<Integer>("by3"){};
> @Override
> public PCollectionTuple expand(PCollection<Integer> input) {
> PCollection<Integer> by2 = input.apply("Filter2s", ParDo.of(new
> FilterFn(2)));
> PCollection<Integer> by3 = input.apply("Filter3s", ParDo.of(new
> FilterFn(3)));
> return PCollectionTuple.of(BY2, by2).and(BY3, by3);
> }
> static class FilterFn extends DoFn<Integer, Integer> {
> private final int divisor;
> FilterFn(int divisor) {
> this.divisor = divisor;
> }
> @ProcessElement
> public void processElement(@Element Integer element,
> OutputReceiver<Integer> r) throws Exception {
> if (element % divisor == 0) {
> r.output(element);
> }
> }
> }
> }
> {code}
>
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