Source.futureSource

Streams the elements of the given future source once it successfully completes.

Source operators

Signature

Source.futureSourceSource.futureSource

Description

Streams the elements of the given future source once it successfully completes. If the future fails the stream is failed.

For the corresponding operator for the Java standard library CompletionStage see completionStageSource.

Example

Suppose we are accessing a remote service that streams user data over HTTP/2 or a WebSocket. We can model that as a Source<User,NotUsed>Source[User,NotUsed] but that source will only be available once the connection has been established.

Scala

copysource
import akka.NotUsed
import akka.stream.scaladsl.Source

import scala.concurrent.Future
object FutureSource {
  def sourceCompletionStageSource(): Unit = {
    val userRepository: UserRepository = ??? // an abstraction over the remote service
    val userFutureSource = Source.futureSource(userRepository.loadUsers)
    // ...
  }

  trait UserRepository {
    def loadUsers: Future[Source[User, NotUsed]]
  }

  case class User()
}

Reactive Streams semantics