The obvious ones are:
1. write your own fsm and embed it in an actor (it's not that hard. I
wasted a quite a lot of time trying to bend the akka one to my purposes
inappropriately before I realised this).
2. consider whether you are ever truly "active". After all you never had
the opportunity to process messages in the active state. In which case
shuffle the active transition processing into a separate method where you
can access from either place. I'm not saying this is appropriate for you.
3. someone in scala-user suggested a self-message. Don't do that if there's
a slightest change another message will arrive (or be in your input queue)
otherwise it will be out of sequence. You might be able to circumvent this
with some multi-actor explicit queue management but for me this was the
first step in the slippery slope that led to wasted time and kept me away
from realising that (1) was best for me.
On Thursday, January 9, 2014 9:32:22 AM UTC, Alexandru Nedelcu wrote:
>
> Hi,
>
> I'm re-posting this from scala-user.
>
> I have a problem with FSM Actors in Akka. Say I have a bunch of states and
> the transitions look something like this:
>
> Waiting -> Active -> Expired
>
> You can't get from Waiting to Expired directly. But when in "Waiting" I
> still need to be able to send an "Expire" message to the actor, at which
> point I need the actor to execute the transition changes for both (Waiting
> -> Active) and for (Active -> Expired).
>
> So I basically want something like this (making stuff up):
>
>
> when(Waiting) {
> case Event(Expire, _) =>
> goto(Active).andThen(Expired)
> }
>
> onTransition {
> case Waiting -> Active => /* activate */
> case Active -> Expired => /* expiry */
> }
>
> This is basically a non-deterministic finite automaton.
>
> Looking at the documentation and in the source-code, I don't believe this
> is possible. It would have been great though, because the goto() on the
> Expire event would make it perfectly clear that the actor first goes into
> Active before being Expired. So what choices do I have?
>
> Thanks,
>
>
>
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