Sink.ignore

Consume all elements but discards them.

Sink operators

Signature

Sink.ignoreSink.ignore

Description

Consume all elements but discards them. Useful when a stream has to be consumed but there is no use to actually do anything with the elements in the Sink. Processing of the elements may occur in the Source/Flow.

Example

This examples reads lines from a file, saves them to a database, and stores the database identifiers in another file. The stream is run with Sink.ignore because all processing of the elements have been performed by the preceding stream operators.

Scala

copysourceval lines: Source[String, NotUsed] = readLinesFromFile()
val databaseIds: Source[UUID, NotUsed] =
  lines.mapAsync(1)(line => saveLineToDatabase(line))
databaseIds.mapAsync(1)(uuid => writeIdToFile(uuid)).runWith(Sink.ignore)

Java

copysourceSource<String, NotUsed> lines = readLinesFromFile();
Source<UUID, NotUsed> databaseIds = lines.mapAsync(1, line -> saveLineToDatabase(line));
databaseIds.mapAsync(1, uuid -> writeIdToFile(uuid)).runWith(Sink.ignore(), system);

Reactive Streams semantics