prepend

Prepends the given source to the flow, consuming it until completion before the original source is consumed.

Fan-in operators

Signature

Source.prependSource.prepend Flow.prependFlow.prepend

Description

Prepends the given source to the flow, consuming it until completion before the original source is consumed.

If materialized values needs to be collected prependMat is available.

Example

Scala

val ladies = Source(List("Emma", "Emily"))
val gentlemen = Source(List("Liam", "William"))

gentlemen.prepend(ladies).runWith(Sink.foreach(println))
// this will print "Emma", "Emily", "Liam", "William"

Java

import akka.stream.javadsl.Source;
import akka.stream.javadsl.Sink;
import java.util.Arrays;

Source<String, NotUsed> ladies = Source.from(Arrays.asList("Emma", "Emily"));
Source<String, NotUsed> gentlemen = Source.from(Arrays.asList("Liam", "William"));
gentlemen.prepend(ladies).runWith(Sink.foreach(System.out::print), system);
// this will print "Emma", "Emily", "Liam", "William"

Reactive Streams semantics