akka.routing.Listeners.scala Maven / Gradle / Ivy

/*
 * Copyright (C) 2009-2020 Lightbend Inc. 
 */

package akka.routing

import java.util.{ Set, TreeSet }

import akka.actor.{ Actor, ActorRef }

sealed trait ListenerMessage
final case class Listen(listener: ActorRef) extends ListenerMessage
final case class Deafen(listener: ActorRef) extends ListenerMessage
final case class WithListeners(f: (ActorRef) => Unit) extends ListenerMessage

/**
 * Listeners is a generic trait to implement listening capability on an Actor.
 * 
 * Use the gossip(msg) method to have it sent to the listeners.
 * 

 * Send Listen(self) to start listening.
 * 

 * Send Deafen(self) to stop listening.
 * 
 * Send WithListeners(fun) to traverse the current listeners.
 */
trait Listeners { self: Actor =>
  protected val listeners: Set[ActorRef] = new TreeSet[ActorRef]

  /**
   * Chain this into the receive function.
   *
   * {{{ def receive = listenerManagement orElse … }}}
   */
  protected def listenerManagement: Actor.Receive = {
    case Listen(l) => listeners.add(l)
    case Deafen(l) => listeners.remove(l)
    case WithListeners(f) =>
      val i = listeners.iterator
      while (i.hasNext) f(i.next)
  }

  /**
   * Sends the supplied message to all current listeners using the provided sender() as sender.
   */
  protected def gossip(msg: Any)(implicit sender: ActorRef = Actor.noSender): Unit = {
    val i = listeners.iterator
    while (i.hasNext) i.next ! msg
  }
}