akka.actor

FSM

trait FSM[S, D] extends Listeners

Finite State Machine actor trait. Use as follows:

  object A {
    trait State
    case class One extends State
    case class Two extends State

    case class Data(i : Int)
  }

  class A extends Actor with FSM[A.State, A.Data] {
    import A._

    startWith(One, Data(42))
    when(One) {
        case Event(SomeMsg, Data(x)) => ...
        case Ev(SomeMsg) => ... // convenience when data not needed
    }
    when(Two, stateTimeout = 5 seconds) { ... }
    initialize
  }

Within the partial function the following values are returned for effecting state transitions:

Each of the above also supports the method replying(AnyRef) for sending a reply before changing state.

While changing state, custom handlers may be invoked which are registered using onTransition. This is meant to enable concentrating different concerns in different places; you may choose to use when for describing the properties of a state, including of course initiating transitions, but you can describe the transitions using onTransition to avoid having to duplicate that code among multiple paths which lead to a transition:

onTransition {
  case Active -> _ => cancelTimer("activeTimer")
}

Multiple such blocks are supported and all of them will be called, not only the first matching one.

Another feature is that other actors may subscribe for transition events by sending a SubscribeTransitionCallback message to this actor; use UnsubscribeTransitionCallback before stopping the other actor.

State timeouts set an upper bound to the time which may pass before another message is received in the current state. If no external message is available, then upon expiry of the timeout a StateTimeout message is sent. Note that this message will only be received in the state for which the timeout was set and that any message received will cancel the timeout (possibly to be started again by the next transition).

Another feature is the ability to install and cancel single-shot as well as repeated timers which arrange for the sending of a user-specified message:

  setTimer("tock", TockMsg, 1 second, true) // repeating
  setTimer("lifetime", TerminateMsg, 1 hour, false) // single-shot
  cancelTimer("tock")
  timerActive_? ("tock")

Self Type
FSM[S, D] with Actor
Linear Supertypes
Listeners, AnyRef, Any
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Type Members

  1. case class Event(event: Any, stateData: D) extends Product with Serializable

  2. type State = State[S, D]

  3. type StateFunction = PartialFunction[Event, State]

  4. case class StopEvent[S, D](reason: Reason, currentState: S, stateData: D) extends Product with Serializable

  5. type Timeout = Option[Duration]

  6. type TransitionHandler = PartialFunction[(S, S), Unit]

Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any
  3. final def ##(): Int

    Definition Classes
    AnyRef → Any
  4. val ->: akka.actor.FSM.->.type

  5. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  6. final def ==(arg0: Any): Boolean

    Definition Classes
    Any
  7. val StateTimeout: akka.actor.FSM.StateTimeout.type

  8. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  9. def cancelTimer(name: String): Unit

    Cancel named timer, ensuring that the message is not subsequently delivered (no race).

    Cancel named timer, ensuring that the message is not subsequently delivered (no race).

    name

    of the timer to cancel

    Attributes
    protected[akka]
  10. def clone(): AnyRef

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  11. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  12. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  13. def finalize(): Unit

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  14. final def getClass(): java.lang.Class[_]

    Definition Classes
    AnyRef → Any
  15. def gossip(msg: Any): Unit

    Attributes
    protected
    Definition Classes
    Listeners
  16. final def goto(nextStateName: S): State

    Produce transition to other state.

    Produce transition to other state. Return this from a state function in order to effect the transition.

    nextStateName

    state designator for the next state

    returns

    state transition descriptor

    Attributes
    protected
  17. def hashCode(): Int

    Definition Classes
    AnyRef → Any
  18. final def initialize: Unit

    Verify existence of initial state and setup timers.

    Verify existence of initial state and setup timers. This should be the last call within the constructor.

    Attributes
    protected
  19. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any
  20. def listenerManagement: Receive

    Attributes
    protected
    Definition Classes
    Listeners
  21. val listeners: ConcurrentSkipListSet[ActorRef]

    Attributes
    protected
    Definition Classes
    Listeners
  22. val log: LoggingAdapter

  23. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  24. def nextStateData: D

    Return next state data (available in onTransition handlers)

    Return next state data (available in onTransition handlers)

    Attributes
    protected[akka]
  25. final def notify(): Unit

    Definition Classes
    AnyRef
  26. final def notifyAll(): Unit

    Definition Classes
    AnyRef
  27. final def onTermination(terminationHandler: PartialFunction[StopEvent[S, D], Unit]): Unit

    Set handler which is called upon termination of this FSM actor.

    Set handler which is called upon termination of this FSM actor.

    Attributes
    protected
  28. final def onTransition(transitionHandler: TransitionHandler): Unit

    Set handler which is called upon each state transition, i.

    Set handler which is called upon each state transition, i.e. not when staying in the same state. This may use the pair extractor defined in the FSM companion object like so:

    onTransition {
      case Old -> New => doSomething
    }
    

    It is also possible to supply a 2-ary function object:

    onTransition(handler _)
    
    private def handler(from: S, to: S) { ... }
    

    The underscore is unfortunately necessary to enable the nicer syntax shown above (it uses the implicit conversion total2pf under the hood).

    Multiple handlers may be installed, and every one of them will be called, not only the first one matching.

    Attributes
    protected
  29. def postStop(): Unit

  30. final def receive: Receive

    Attributes
    protected
  31. final def setStateTimeout(state: S, timeout: Timeout): Unit

    Set state timeout explicitly.

    Set state timeout explicitly. This method can safely be used from within a state handler.

    Attributes
    protected
  32. def setTimer(name: String, msg: Any, timeout: Duration, repeat: Boolean): State

    Schedule named timer to deliver message after given delay, possibly repeating.

    Schedule named timer to deliver message after given delay, possibly repeating.

    name

    identifier to be used with cancelTimer()

    msg

    message to be delivered

    timeout

    delay of first message delivery and between subsequent messages

    repeat

    send once if false, scheduleAtFixedRate if true

    returns

    current state descriptor

    Attributes
    protected[akka]
  33. final def startWith(stateName: S, stateData: D, timeout: Timeout = None): Unit

    Set initial state.

    Set initial state. Call this method from the constructor before the #initialize method.

    stateName

    initial state designator

    stateData

    initial state data

    timeout

    state timeout for the initial state, overriding the default timeout for that state

    Attributes
    protected
  34. def stateData: D

    Return current state data (i.

    Return current state data (i.e. object of type D)

    Attributes
    protected[akka]
  35. def stateName: S

    Return current state name (i.

    Return current state name (i.e. object of type S)

    Attributes
    protected[akka]
  36. final def stay(): State

    Produce "empty" transition descriptor.

    Produce "empty" transition descriptor. Return this from a state function when no state change is to be effected.

    returns

    descriptor for staying in current state

    Attributes
    protected
  37. final def stop(reason: Reason, stateData: D): State

    Produce change descriptor to stop this FSM actor including specified reason.

    Produce change descriptor to stop this FSM actor including specified reason.

    Attributes
    protected
  38. final def stop(reason: Reason): State

    Produce change descriptor to stop this FSM actor including specified reason.

    Produce change descriptor to stop this FSM actor including specified reason.

    Attributes
    protected
  39. final def stop(): State

    Produce change descriptor to stop this FSM actor with reason "Normal".

    Produce change descriptor to stop this FSM actor with reason "Normal".

    Attributes
    protected
  40. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  41. final def timerActive_?(name: String): Boolean

    Inquire whether the named timer is still active.

    Inquire whether the named timer is still active. Returns true unless the timer does not exist, has previously been canceled or if it was a single-shot timer whose message was already received.

    Attributes
    protected[akka]
  42. def toString(): String

    Definition Classes
    AnyRef → Any
  43. implicit final def total2pf(transitionHandler: (S, S) ⇒ Unit): PartialFunction[(S, S), Unit]

    Convenience wrapper for using a total function instead of a partial function literal.

    Convenience wrapper for using a total function instead of a partial function literal. To be used with onTransition.

    Attributes
    protected
  44. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  45. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  46. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  47. final def when(stateName: S, stateTimeout: Duration = null)(stateFunction: StateFunction): Unit

    Insert a new StateFunction at the end of the processing chain for the given state.

    Insert a new StateFunction at the end of the processing chain for the given state. If the stateTimeout parameter is set, entering this state without a differing explicit timeout setting will trigger a StateTimeout event; the same is true when using #stay.

    stateName

    designator for the state

    stateTimeout

    default state timeout for this state

    stateFunction

    partial function describing response to input

    Attributes
    protected
  48. final def whenUnhandled(stateFunction: StateFunction): Unit

    Set handler which is called upon reception of unhandled messages.

    Set handler which is called upon reception of unhandled messages.

    Attributes
    protected

Deprecated Value Members

  1. final def when(stateName: S, stateTimeout: Timeout)(stateFunction: StateFunction): Unit

    Attributes
    protected
    Annotations
    @deprecated
    Deprecated

    (Since version 2.0) use the more import-friendly variant taking a Duration

Inherited from Listeners

Inherited from AnyRef

Inherited from Any