scala中的self type

scala目前的书籍有两《快学scala》和《scala编程》。资料确实不多，对这个语法使用只能结合使用进行理解。

先看源码：

private[spark] trait ActorLogReceive {

  self: Actor =>

  override def receive: Actor.Receive = new Actor.Receive {

    private val _receiveWithLogging = receiveWithLogging

    override def isDefinedAt(o: Any): Boolean = {

      val handled = _receiveWithLogging.isDefinedAt(o)

      if (!handled) {

        log.debug(s"Received unexpected actor system event: $o")

      }

      handled

    }

    override def apply(o: Any): Unit = {

      if (log.isDebugEnabled) {

        log.debug(s"[actor] received message $o from ${self.sender}")

      }

      val start = System.nanoTime

      _receiveWithLogging.apply(o)

      val timeTaken = (System.nanoTime - start).toDouble / 1000000

      if (log.isDebugEnabled) {

        log.debug(s"[actor] handled message ($timeTaken ms) $o from ${self.sender}")

      }

    }

  }

  def receiveWithLogging: Actor.Receive

  protected def log: Logger

}

这块代码是spark的akka日志记录代码，很具有代表性，self:Actor =>这里有两个作用

1: ActorLogReceive的实现类必须继承Actor

2: 重写Actor里面的方法，该trait里面使用Actor里面的属性不要添加self.

本理实现一种代理，或是模板模式....

来看看他的使用

    lazy val actorRef = actorSystem.actorOf(Props(new Actor with ActorLogReceive with Logging{

      override def receiveWithLogging: Receive = ???

    }))

巴特西

scala中的self type

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