PingPong Akka intro example

PingPong.scala

import akka.actor._

/** The messages that the Ping actor responds to */
object PingProtocol {
  case object StartMessage
  case object PongMessage
}

/** The messages that the Pong actor responds to */
object PongProtocol {
  case object PingMessage
  case object StopMessage
}

/**
 * An Akka Actor example written by Alvin Alexander of
 * http://devdaily.com
 *
 * Shared here under the terms of the Creative Commons
 * Attribution Share-Alike License: http://creativecommons.org/licenses/by-sa/2.5/
 * 
 * more akka info: http://doc.akka.io/docs/akka/snapshot/scala/actors.html
 */
class Ping(pong: ActorRef) extends Actor {
  import PingProtocol._
  import PongProtocol._
  var count = 0
  def incrementAndPrint { count += 1; println("ping - Thread %s:".format(Thread.currentThread.getName)) }
  def receive = {
    case StartMessage =>
        incrementAndPrint
        pong ! PingMessage
    case PongMessage => 
        incrementAndPrint
        if (count > 99) {
          sender ! StopMessage
          println("ping stopped")
          context.stop(self)
        } else {
          sender ! PingMessage
        }
  }
}

class Pong extends Actor {
  import PingProtocol._
  import PongProtocol._
  def receive = {
    case PingMessage =>
        println("  pong - Thread %s:".format(Thread.currentThread.getName))
        sender ! PongMessage
    case StopMessage =>
        println("pong stopped")
        context.stop(self)
  }
}

object PingPongTest extends App {
  val system = ActorSystem("PingPongSystem")
  val pong = system.actorOf(Props[Pong], name = "pong")
  val ping = system.actorOf(Props(new Ping(pong)), name = "ping")
  // start them going
  ping ! PingProtocol.StartMessage
  // shutdown - important to call this from the REPL so that the REPL can be closed cleanly
  system.shutdown
}