Question

How do I run 2 Akka actors with the caller sending the consumer a message every n seconds?
As there are no loop-react methods as in the Scala.Actors library I am stuck
somehow, the following will not compile and produces:

overriding method receive in trait Actor of type =>
Caller.this.Receive; method receive has incompatible type

object Foo {
  def init() {
    actorOf[Caller].start()
    actorOf[Consumer].start()
  }
}

class Caller extends Actor {

  def receive {
    while (true) {
      self ! "msg"
      Thread.sleep(1000)
    }
  }
}

class Consumer extends Actor {

  def receive = {
    case msg:String => doStuff()
    case e => _
  }
}

Answer 1

You’re missing the equals sign after receive in Caller. Without it, the method is defined as returning Unit (i.e. no useful value), and akka needs you to return a PartialFunction[Any,Unit] from receive.

Now, to actually implement your logic in the idiomatic way, you probably want to use a ReceiveTimeout, like so:

class Caller extends Actor {
  self.receiveTimeout = Some(1000)

  def receive = { 
    case ReceiveTimeout => 
      self ! "msg"
  }
}