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

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

Java

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

Reactive Streams semantics