optionalVia

For a stream containing optional elements, transforms each element by applying the given viaFlow and passing the value downstream as an optional value.

Simple operators

Signature

Source.optionalVia Flow.optionalVia

Description

For a stream containing optional elements, transforms each element by applying the given viaFlow and passing the value downstream as an optional value.

Scala
Java
sourceSource.optionalVia(
  Source(List(Some("1"), None, None, Some("4"))),
  Flow.fromFunction { (string: String) => string.toInt }
)(Keep.none).runForeach(println)
// Some(1)
// None
// None
// Some(4)
sourceFlow<String, Integer, NotUsed> flow = Flow.fromFunction(Integer::parseInt);

Source<Optional<String>, NotUsed> source =
    Source.from(
        Arrays.asList(Optional.of("1"), Optional.empty(), Optional.empty(), Optional.of("4")));

Source.optionalVia(source, flow, Keep.none()).runForeach(System.out::println, system);
// Optional[1]
// Optional.empty
// Optional.empty
// Optional[4]

Reactive Streams semantics

emits while the provided viaFlow is runs with defined elements

backpressures when the viaFlow runs for the defined elements and downstream backpressures

completes when the upstream completes

1.1.3