如何与Akka演员一起使用可堆叠特征模式？ [英] How to use stackable trait pattern with Akka actors?

问题描述

我正在尝试使用可堆叠特征将Pub / Sub特征与其他Akka演员混合使用。

I'm trying to implement a Pub/Sub trait to mix into other akka actors using a stackable trait.

这是我想出的：

trait PubSubActor extends Actor {
  abstract override def receive = 
    super.receive orElse {
      case Subscribe(topic) => /* ... */
      case Publish(topic, msg) => /* ... */
    }
}

class MyActor extends Actor with PubSubActor {
  override def receive = {
    case SomeMessage(a, b, c) => /* ... */
  }
}

编译器抛出一个错误：
错误：在特征MyActor中覆盖方法receive ...方法receive需要`抽象覆盖'修饰符。

At which point, the compiler throws back an error: error: overriding method receive in trait MyActor... method receive needs `abstract override' modifiers.

您能解释一下吗我为什么这不起作用？

Can you explain to me why this isn't working? How can I fix it so it works?

谢谢！

更新

以下作品：

trait PubSubActor extends Actor {
  abstract override def receive = 
    super.receive orElse {
      case Subscribe(topic) => /* ... */
      case Publish(topic, msg) => /* ... */
    }
}

class MyActor extends Actor {
  override def receive = {
    case SomeMessage(a, b, c) => /* ... */
  }
}

class MyActorImpl extends MyActor with PubSubActor

但是为什么呢？为什么我可以通过这种方式获得想要的行为，而没有另一种？有什么原因吗？我似乎无法弄清楚这两个示例之间的根本差异，从而有所作为。

But why? Why can I get the behavior I want this way but not the other? Any reasons? I can't seem to figure out the underlying difference between these two samples that makes the difference.

推荐答案

有一个简单明了的方法解决方案：

There's a simple and concise solution:

使用 orElse 定义链接多个接收函数的接收特征：

Define a Receiving trait that chains multiple receive functions using orElse :

trait Receiving { 
  var receivers: Receive = Actor.emptyBehavior 
  def receiver(next: Actor.Receive) { receivers = receivers orElse next }
  def receive = receivers // Actor.receive definition
}

使用在参与者中，这很容易：

Using this in actors is easy:

trait PubSubActor extends Receiving {
  receiver {
    case Publish => /* I'm the first to handle messages */
  }
}

class MyActor extends PubSubActor with Receiving {
  receiver {
    case SomeMessage => /* PubSubActor didn't handle, I receive the message */ 
  }
}

第一个PubSubActor的接收将被调用。如果未处理该消息，它将被传递到MyActor的接收项。

First PubSubActor's receive will be called. If message wasn't handled it will be passed to MyActor's receive.

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