Sink.lastOption

Materialize a Future[Option[T]] CompletionStage<Optional<T>> which completes with the last value emitted wrapped in an Some Optional when the stream completes.

Sink operators

Signature¶

Sink.lastOptionSink.lastOption

Description¶

Materialize a Future[Option[T]] CompletionStage<Optional<T>> which completes with the last value emitted wrapped in an Some Optional when the stream completes. if the stream completes with no elements the CompletionStage is completed with None an empty Optional.

Example¶

Scala

Java

copysourceval source = Source.empty[Int]
val result: Future[Option[Int]] = source.runWith(Sink.lastOption)
result.map(println)
// None

copysourceSource<Integer, NotUsed> source = Source.empty();
CompletionStage<Optional<Integer>> result = source.runWith(Sink.lastOption(), system);
result.thenAccept(System.out::println);
// Optional.empty

Reactive Streams semantics¶