Chaining Akka actor receive() methods

Sometimes when writing Akka actors you want to mix in traits that also handle incoming messages. The problem is that if you define Actor.receive in a trait you can no longer define it in traits.

To solve this one can define a Receiving trait that chains multiple receive functions using orElse :

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

Using this in actors with traits is easy:

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

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

Alternative solutions available in the docs