Multiple ways to communicate with Akka Actor from outside the system?

Question

I was under the impression that the only way to communicate with an Akka Actor from outside the ActorSystem was via Inbox. However I just found this snippet from Akka's own documentation which shows:

greeter.tell(new WhoToGreet("akka"), ActorRef.noSender());
inbox.send(greeter, new Greet());

So which is it? Is it in fact possible to directly tell an Actor from the outside world, or did Typesafe have a careless intern writing their documentation for them?!?

If it is possible, then when should you do this, and when should you use Inbox? For instance, is one method "fire-and-forget" asynchronous/non-blocking and the other synchronous/blocking?

Answer 1

Inbox is part of the relatively recent Actor DSL API that is "some nice sugar on top of the usual ways to create actors". You can either use the standard way to create / communicate with actors or use the Actor DSL. They are both async. The Actor DSL is nice for creating one-off actors whose lifetime is one method. The advantage of the DSL syntax is a bit more evident in Scala.