http://www.slideshare.net/ktoso/the-need-for-async-scalaworld

console.scala

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_25).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import akka.actor.ActorSystem
import akka.actor.ActorSystem

scala> import akka.stream.ActorMaterializer
import akka.stream.ActorMaterializer

scala> import akka.stream.scaladsl.{Source, Flow, Sink}
import akka.stream.scaladsl.{Source, Flow, Sink}

scala> implicit val actorSystem = ActorSystem("akka-system")
actorSystem: akka.actor.ActorSystem = akka://akka-system

scala> implicit val mat = ActorMaterializer()
mat: akka.stream.ActorMaterializer = ActorMaterializerImpl(akka://akka-system,akka.stream.ActorMaterializerSettings@e60e1fe,akka.dispatch.Dispatchers@28f3bfda,Actor[akka://akka-system/user/$a#121836947],false,0,flow,Optimizations(false,false,false,false))

scala> val fives = Source.repeat(5)
fives: akka.stream.scaladsl.Source[Int,Unit] = akka.stream.scaladsl.Source@65cb4483

scala> val timesTwo = Flow[Int].map(_ * 2)
timesTwo: akka.stream.scaladsl.Flow[Int,Int,Unit] = akka.stream.scaladsl.Flow@214e022a

scala> val intToString = Flow[Int].map(_.toString)
intToString: akka.stream.scaladsl.Flow[Int,String,Unit] = akka.stream.scaladsl.Flow@2ceb64c2

scala> val transform = timesTwo via intToString
transform: akka.stream.scaladsl.Flow[Int,String,Unit] = akka.stream.scaladsl.Flow@4e367162

scala> val sysOut = Sink.foreach(println)
sysOut: akka.stream.scaladsl.Sink[Any,scala.concurrent.Future[Unit]] = akka.stream.scaladsl.Sink@6d626983

scala> val r = fives via transform.take(10) to sysOut
r: akka.stream.scaladsl.RunnableGraph[Unit] =
RunnableGraph(
 Module: repeat
 Modules:    repeat
   mapConcat
   map
   akka.stream.impl.StreamLayout$CopiedModule
 Downstreams:
    RepeatSource.out -> Flow.in
   Flow.out -> Flow.in
   Flow.out -> Flow.in
 Upstreams:
    Flow.in -> RepeatSource.out
   Flow.in -> Flow.out
   Flow.in -> Flow.out
      )

scala> r.run()

scala> 10
10
10
10
10
10
10
10
10
10

example.scala

// http://www.slideshare.net/ktoso/the-need-for-async-scalaworld
// page 126

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.{Source, Flow, Sink}

object Example {

  implicit val actorSystem = ActorSystem("akka-system")
  implicit val mat         = ActorMaterializer()

  val fives = Source.repeat(5)

  val timesTwo = Flow[Int].map(_ * 2)
  val intToString = Flow[Int].map(_.toString)
  val transform = timesTwo via intToString
  val sysOut = Sink.foreach(println)

  val r = fives via transform.take(10) to sysOut

  r.run()
}