scala：asInstanceOf []没有可用的共同祖先

Question

I created some case classes used as messages in akka. When the program receives some messages, it calls the method asInstanceOf[] , but I don't know what to put inside the brackets, as the message can be one of the 3 differents case classes.

here is a try :

abstract class Retour
case class Naissance(val sender : ActorRef) extends Retour
case class NaissanceEtMort(val sender : ActorRef) extends Retour
case class PlusUnMoisOK(val sender : ActorRef) extends Retour

but at the execution of my program I get this error message:

lapins.Clapier$PlusUnMoisOK$ cannot be cast to lapins.Clapier$Retour   

can you help me?

EDIT:

the line of the error is those with [Retour] in :

val future = ask(couple,PlusUnMois)
val result = Await.result(future,timeout.duration).asInstanceOf[Retour]

and the error is below:

[ERROR] [07/02/2015 01:33:48.436] [clapier-akka.actor.default-dispatcher-5] [akka://clapier/user/$a] lapins.Clapier$PlusUnMoisOK$ cannot be cast to lapins.Clapier$Retour
akka.actor.ActorInitializationException: exception during creation

EDIT2:

resolved! the message sending was incorrectly written : indeed, I wrote "sender ! PlusUnMoisOK" instead of "sender ! PlusUnMoisOK(self)"

Answer 1

You could pattern match on the result of the future. Something like:

Await.result(future, timeout.duration) match {
  case n: Naissance => // ...
  case nm: NaissanceEtMort => // ...
  case pm: PlusUnMoisOK => // ...
}

Answer 2

With:

ask(couple,PlusUnMois)

You are sending the class PlusUnMois as a message. If you are doing the same in your couple actor Await.result is returning the class PlusUnMois not an object of PlusUnMois . Trying to cast the class PlusUnMois to Retour results to an error. Try sending an instance of PlusUnMois , like:

val future = ask(couple,new PlusUnMois(someActorRef))

The same should be done in your couple actor:

sender ! new PlusUnMois(someOtherActorRef)

Moreover, instead of using asInstanceOf consider using pattern matching:

 Await.result(future,timeout.duration) match {
   case m : Naissance => // do something Naissance
   case m : NaissanceEtMort => // do something NaissanceEtMort
   case m : PlusUnMoisOK => // do something PlusUnMoisOK
 }