Programming in Scala ch30 (Actor..

scala> self ! "hello"

scala>  self.receive { case x => x }

res9: Any = hello

30.4        线程复用以提高性能（P613）

由于react方法不需要返回，其实现就无需保存当前线程的调用栈，所以当前线程可以被下一个唤醒的actor所使用。该方法很高效，如果程序中所有actor都使用react方法而不是receive方法，只需一个线程就可以处理程序所有的actor（如果计算机是多核CPU，actor就会生成足够多的线程以充分利用CPU所有的核）。

  import actors._, actors.Actor._, java.net._

  object NameResolver extends Actor { // 得到域名对应的ip

    def act() {

      react {

        case (name: String, actor: Actor) => actor ! getIp(name); act()

        case "EXIT" => println("Name resolver exiting.")

        case msg => println("Unhandled message: " + msg); act()

      }

    }

    def getIp(name: String): Option[InetAddress] = {

      try { Some(InetAddress.getByName(name))

      } catch { case _: UnknownHostException => None }

    }

  }

scala> self.receiveWithin(0) { case x => x }

res3: Any = Some(www.scala-lang.org/128.178.154.159)

scala> NameResolver ! ("wwwwww.scala-lang.org", self)

scala> self.receiveWithin(0) { case x => x }        

res5: Any = None

  def act() {

    loop {

      react {

        case (name: String, actor: Actor) => actor ! getIp(name)

        case msg => println("Unhandled message: " + msg)

      }

    }