如何使用 Continuations 拆分和分派异步控制流? [英] How to split and dispatch an async control-flow using Continuations?

问题描述

我有一个像下面这样的异步控制流:

I have an asynchronous control-flow like the following:

ActorA ! DoA(dataA, callback1, callbackOnErrorA)

def callback1() = {
  ...
  ActorB ! DoB(dataB, callback2, callbackOnErrorB)
}

def callback2() = {
  ActorC ! DoC(dataC, callback3, callbackOnErrorC)
} 

...

我如何将这个流分成几个部分(延续)，并在保持整体状态的同时将它们按顺序分派给不同的参与者(或线程/任务)?

How would I divide this flow into several parts (continuations) and sequentially dispatch these to different actors (or threads/tasks) while maintaining the overall state?

感谢任何提示，谢谢

推荐答案

这非常简化，但展示了如何在三个参与者之间拆分单个控制流，将状态传递给每个参与者:

This is very simplified, but shows how to split up a single control flow among three actors, passing the state along to each:

package blevins.example

import scala.continuations._
import scala.continuations.ControlContext._
import scala.actors.Actor._
import scala.actors._

object App extends Application {

  val actorA, actorB, actorC = actor {
    receive {
      case f: Function1[Unit,Unit] => { f() }
    }
  }

  def handle(a: Actor) = shift { k: (Unit=>Unit) =>
    a ! k
  }

  // Control flow to split up
  reset {
      // this is not handled by any actor
      var x = 1
      println("a: " + x)

      handle(actorA)  // actorA handles the below
      x += 4
      println("b: " + x)

      handle(actorB) // then, actorB handles the rest
      var y = 2
      x += 2
      println("c: " + x)

      handle(actorC) // and so on...
      y += 1
      println("d: " + x + ":" + y)
  }

}

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