I've implemented a Listenable/Listener trait that can be added to Actors. I'm wondering if it's possible to attach this style of trait to an actor without it having to explicitly call the listenerHandler method?

Also I was expecting to find this functionality in the Akka library. Am I missing something or is there some reason that Akka would not not include this?

trait Listenable { this: Actor =>
    private var listeners: List[Actor] = Nil

    protected def listenerHandler: PartialFunction[Any, Unit] = {
        case AddListener(who) => listeners = who :: listeners
    }

    protected def notifyListeners(event: Any) = {
        listeners.foreach(_.send(event))
    }
}

class SomeActor extends Actor with Listenable
{
    def receive = listenerHandler orElse {
        case Start => notifyListeners(Started())
        case Stop => notifyListeners(Stopped())
    }
}