如何开始一个 Scala akka 演员

How to start a Scala akka actor

提问by blue-sky

Below class is causing an error at line new HelloWorld :

下面的类在 new HelloWorld 行导致错误：

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)

So I try : val hw = actorOf(new HelloWorld)But this causes a compiler error :

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

not found: value actorOf

How should HelloWorld below be implemented ?

下面的HelloWorld应该如何实现？

Reading other Scala docs an act method is requried to be defined within the class that extends Actor and then invoke the start method on this class, is there a reason for using actorOf instead of defining an act method ?

阅读其他 Scala 文档，需要在扩展 Actor 的类中定义一个行为方法，然后在这个类上调用 start 方法，是否有理由使用 actorOf 而不是定义一个行为方法？

Below class is taken from Scala akka docs http://doc.akka.io/docs/akka/2.2.0/scala.html:

下面的课程取自 Scala akka 文档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
    }

}

回答by Jatin

You need to edit your main as shown below. Secondly, in line-5, you need to change it to context.actorOf(Props(new Greeter)). This is because your Greeterdoes not have applyfunction defined, hence you need to manually create Greeter object yourself.

您需要编辑您的主要内容，如下所示。其次，在第 5 行，您需要将其更改为context.actorOf(Props(new Greeter)). 这是因为您Greeter没有apply定义函数，因此您需要自己手动创建 Greeter 对象。

Working code below:

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])
    }

}

回答by some some

If you want to use your main class do the following:

如果要使用主类，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")
}

Which will create a new actor system and then create the HelloWorld actor using that actor system.

这将创建一个新的演员系统，然后使用该演员系统创建 HelloWorld 演员。

You can also follow the akka instructions: set Akka.Main as the main class and give the program "com.example.HelloWorld" as argument.

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

回答by Shiva Komat

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

I don't think you need to have a new keyword there for Greeter. I believe the Props does that for you already. If anything having a new should be a

我认为您不需要为 Greeter 设置一个新关键字。我相信 Props 已经为你做到了。如果任何有新的东西应该是