80 lines
3.7 KiB
ReStructuredText
80 lines
3.7 KiB
ReStructuredText
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.. _actordsl-scala:
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################
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Actor DSL
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################
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The Actor DSL
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=============
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Simple actors—for example one-off workers or even when trying things out in the
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REPL—can be created more concisely using the :class:`Act` trait. The supporting
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infrastructure is bundled in the following import:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#import
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This import is assumed for all code samples throughout this section. The
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implicit actor system serves as :class:`ActorRefFactory` for all examples
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below. To define a simple actor, the following is sufficient:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#simple-actor
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Here, :meth:`actor` takes the role of either ``system.actorOf`` or
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``context.actorOf``, depending on which context it is called in: it takes an
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implicit :class:`ActorRefFactory`, which within an actor is available in the
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form of the ``implicit val context: ActorContext``. Outside of an actor, you’ll
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have to either declare an implicit :class:`ActorSystem`, or you can give the
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factory explicitly (see further below).
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The two possible ways of issuing a ``context.become`` (replacing or adding the
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new behavior) are offered separately to enable a clutter-free notation of
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nested receives:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#becomeStacked
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Please note that calling ``unbecome`` more often than ``becomeStacked`` results
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in the original behavior being installed, which in case of the :class:`Act`
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trait is the empty behavior (the outer ``become`` just replaces it during
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construction).
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Life-cycle management
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---------------------
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Life-cycle hooks are also exposed as DSL elements (see :ref:`start-hook-scala` and :ref:`stop-hook-scala`), where later invocations of the methods shown below will replace the contents of the respective hooks:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#simple-start-stop
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The above is enough if the logical life-cycle of the actor matches the restart
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cycles (i.e. ``whenStopping`` is executed before a restart and ``whenStarting``
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afterwards). If that is not desired, use the following two hooks (see :ref:`restart-hook-scala`):
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#failing-actor
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It is also possible to create nested actors, i.e. grand-children, like this:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#nested-actor
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.. note::
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In some cases it will be necessary to explicitly pass the
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:class:`ActorRefFactory` to the :meth:`actor()` method (you will notice when
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the compiler tells you about ambiguous implicits).
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The grand-child will be supervised by the child; the supervisor strategy for
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this relationship can also be configured using a DSL element (supervision
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directives are part of the :class:`Act` trait):
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#supervise-with
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Actor with :class:`Stash`
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-------------------------
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Last but not least there is a little bit of convenience magic built-in, which
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detects if the runtime class of the statically given actor subtype extends the
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:class:`RequiresMessageQueue` trait via the :class:`Stash` trait (this is a
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complicated way of saying that ``new Act with Stash`` would not work because its
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runtime erased type is just an anonymous subtype of ``Act``). The purpose is to
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automatically use the appropriate deque-based mailbox type required by :class:`Stash`.
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If you want to use this magic, simply extend :class:`ActWithStash`:
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.. includecode:: ../../../akka-actor-tests/src/test/scala/akka/actor/ActorDSLSpec.scala#act-with-stash
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