Packages

abstract class ActorRef extends Comparable[ActorRef] with Serializable

Immutable and serializable handle to an actor, which may or may not reside on the local host or inside the same akka.actor.ActorSystem. An ActorRef can be obtained from an akka.actor.ActorRefFactory, an interface which is implemented by ActorSystem and akka.actor.ActorContext. This means actors can be created top-level in the ActorSystem or as children of an existing actor, but only from within that actor.

ActorRefs can be freely shared among actors by message passing. Message passing conversely is their only purpose, as demonstrated in the following examples:

Scala:

import akka.pattern.ask
import scala.concurrent.Await

class ExampleActor extends Actor {
  val other = context.actorOf(Props[OtherActor], "childName") // will be destroyed and re-created upon restart by default

  def receive {
    case Request1(msg) => other ! refine(msg)     // uses this actor as sender reference, reply goes to us
    case Request2(msg) => other.tell(msg, sender()) // forward sender reference, enabling direct reply
    case Request3(msg) =>
      implicit val timeout = Timeout(5.seconds)
      (other ? msg) pipeTo sender()
      // the ask call will get a future from other's reply
      // when the future is complete, send its value to the original sender
  }
}

Java:

import static akka.pattern.Patterns.ask;
import static akka.pattern.Patterns.pipe;

public class ExampleActor extends UntypedActor {
  // this child will be destroyed and re-created upon restart by default
  final ActorRef other = getContext().actorOf(Props.create(OtherActor.class), "childName");

  @Override
  public void onReceive(Object o) {
    if (o instanceof Request1) {
      Msg msg = ((Request1) o).getMsg();
      other.tell(msg, getSelf()); // uses this actor as sender reference, reply goes to us

    } else if (o instanceof Request2) {
      Msg msg = ((Request2) o).getMsg();
      other.tell(msg, getSender()); // forward sender reference, enabling direct reply

    } else if (o instanceof Request3) {
      Msg msg = ((Request3) o).getMsg();
      pipe(ask(other, msg, 5000), context().dispatcher()).to(getSender());
      // the ask call will get a future from other's reply
      // when the future is complete, send its value to the original sender

    } else {
      unhandled(o);
    }
  }
}

ActorRef does not have a method for terminating the actor it points to, use akka.actor.ActorRefFactory.stop(ref), or send a akka.actor.PoisonPill, for this purpose.

Two actor references are compared equal when they have the same path and point to the same actor incarnation. A reference pointing to a terminated actor doesn't compare equal to a reference pointing to another (re-created) actor with the same path.

If you need to keep track of actor references in a collection and do not care about the exact actor incarnation you can use the ActorPath as key because the unique id of the actor is not taken into account when comparing actor paths.

Self Type
InternalActorRef
Source
ActorRef.scala
Linear Supertypes
Serializable, Serializable, Comparable[ActorRef], AnyRef, Any
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Inherited
  1. ActorRef
  2. Serializable
  3. Serializable
  4. Comparable
  5. AnyRef
  6. Any
Implicitly
  1. by actorRef2Scala
  2. by any2stringadd
  3. by StringFormat
  4. by Ensuring
  5. by ArrowAssoc
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Visibility
  1. Public
  2. All

Instance Constructors

  1. new ActorRef()

Abstract Value Members

  1. abstract def path: ActorPath

    Returns the path for this actor (from this actor up to the root actor).

Concrete Value Members

  1. def !(message: Any)(implicit sender: ActorRef = Actor.noSender): Unit

    Sends a one-way asynchronous message.

    Sends a one-way asynchronous message. E.g. fire-and-forget semantics.

    If invoked from within an actor then the actor reference is implicitly passed on as the implicit 'sender' argument.

    This actor 'sender' reference is then available in the receiving actor in the 'sender()' member variable, if invoked from within an Actor. If not then no sender is available. 

      actor ! message

    Implicit
    This member is added by an implicit conversion from ActorRef to ScalaActorRef performed by method actorRef2Scala in akka.actor.
    Definition Classes
    ScalaActorRef
  2. final def compareTo(other: ActorRef): Int

    Comparison takes path and the unique id of the actor cell into account.

    Comparison takes path and the unique id of the actor cell into account.

    Definition Classes
    ActorRef → Comparable
  3. final def equals(that: Any): Boolean

    Equals takes path and the unique id of the actor cell into account.

    Equals takes path and the unique id of the actor cell into account.

    Definition Classes
    ActorRef → AnyRef → Any
  4. def forward(message: Any)(implicit context: ActorContext): Unit

    Forwards the message and passes the original sender actor as the sender.

    Forwards the message and passes the original sender actor as the sender.

    Works, no matter whether originally sent with tell/'!' or ask/'?'.

  5. final def hashCode(): Int
    Definition Classes
    ActorRef → AnyRef → Any
  6. final def tell(msg: Any, sender: ActorRef): Unit

    Sends the specified message to this ActorRef, i.e.

    Sends the specified message to this ActorRef, i.e. fire-and-forget semantics, including the sender reference if possible.

    Pass akka.actor.ActorRef noSender or null as sender if there is nobody to reply to

  7. def toString(): String
    Definition Classes
    ActorRef → AnyRef → Any