Question

下面的类在新的HelloWorld行引起错误：

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

以下HelloWorld应如何实施？

读取其他Scala文档时，需要在扩展Actor的类中定义act方法，然后在此类上调用start方法，是否有理由使用actorOf而不是定义act方法？

以下课程摘自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

您需要编辑主页，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。

以下工作代码：

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])
    }

}

Answer 2

如果您想使用您的主类，请执行以下操作：

import akka.actor.{ActorSystem, Props}
object Driver extends App {    
    val system = ActorSystem("System")
    val hw = system.actorOf(Props[HelloWorld], name = "hw")
}

这将创建一个新的actor系统，然后使用该actor系统创建HelloWorld actor。

您还可以按照akka说明操作：将Akka.Main设置为主类，并将程序“com.example.HelloWorld”作为参数。

Answer 3

val greeter = context.actorOf(Props(new Greeter), "greeter")//line 5

我认为你不需要为Greeter提供新的关键字。我相信道具已经为你做到了。如果有任何新的东西应该是

如何开始Scala akka演员

3 个答案: