如何启动Scala akka actor

Question

class下导致new HelloWorld行出现错误：

Exception in thread "main" akka.actor.ActorInitializationException: You cannot create an instance of [HelloWorld] explicitly using the constructor (new). You have to use one of the 'actorOf' factory methods to create a new actor. See the documentation.
  at akka.actor.ActorInitializationException$.apply(Actor.scala:219)
  at akka.actor.Actor$class.$init$(Actor.scala:436)
  at HelloWorld.<init>(HelloWorld.scala:4)
  at Driver$.main(HelloWorld.scala:38)
  at Driver.main(HelloWorld.scala)

所以我尝试:val hw=actorOf(new HelloWorld)，但这会导致编译器错误：

not found: value actorOf

下面的HelloWorld应该如何实现？

阅读其他Scala文档时，要求在扩展Actor的类中定义act方法，然后在该类上调用start方法，是否有理由使用actorOf而不是定义act方法？

以下内容摘自Scala akka docs http://doc.akka.io/docs/akka/2.2.0/Scala.html:

import akka.actor.Actor
import akka.actor.Actor._
import akka.actor.Props

class HelloWorld extends Actor {

  override def preStart(): Unit = {
    // create the greeter actor
    val greeter = context.actorOf(Props[Greeter], "greeter")
    // tell it to perform the greeting
    greeter ! Greeter.Greet
  }
  def receive = {
    // when the greeter is done, stop this actor and with it the application
    case Greeter.Done => context.stop(self)
  }

  object Greeter {   

    case object Greet
    case object Done


  }
  class Greeter extends Actor {
    def receive = {
      case Greeter.Greet =>
        println("Hello World!")
        sender ! Greeter.Done
    }
  }


}

object Driver {

    def main(args: Array[String]) {
      new HelloWorld
    }

}

Answer 1

你需要编辑你的主，如下所示。其次，在第5行中，您需要将其更改为context.actorof（Props（new Greeter））。这是因为您的Greeter没有定义apply函数，因此您需要自己手动创建Greeter对象。

工作代码如下：

import akka.actor.ActorSystem

class HelloWorld extends Actor {

  override def preStart(): Unit = {
    // create the greeter actor
    val greeter = context.actorOf(Props(new Greeter), "greeter")//line 5
    // tell it to perform the greeting
    greeter ! Greeter.Greet
  }
  def receive = {
    // when the greeter is done, stop this actor and with it the application
    case Greeter.Done => context.stop(self)
  }

  object Greeter {   

    case object Greet
    case object Done


  }
  class Greeter extends Actor {
    def receive = {
      case Greeter.Greet =>
        println("Hello World!")
        sender ! Greeter.Done
    }
  }


}

object Driver {

    def main(args: Array[String]) {
      val system = ActorSystem("Main")
      val ac = system.actorOf(Props[HelloWorld])
    }

}