Technically it may be safe in that case, you're in an Actor after all.
However I'd argue it's bad style as it mixes an API designed for immutable data
passing (the data param of FSM),
in a mutable way, which can/will lead to confusion when someone else reads your
code.
If you want to have (or are forced to by some API that exposes such) mutable
state, just keel a variable in the Actor's body.
Also remember that in general:
"mutable reference to immutable data" is better than "immutable reference to
mutable data",
since the danger of leaking the object in a message is not an issue in the
first case.
--
Cheers,
Konrad 'ktoso’ Malawski
Akka @ Typesafe
On 30 January 2016 at 04:47:27, James P (jsp0...@gmail.com) wrote:
Hi folks,
Good day. I'm just starting with Akka (Java with Lambda) and I have a question
regarding AbstractFSM.
When using "akka.actor.FSM.State.using(Data)" does "Data" need to be immutable?
Example:
when(State.Idle,
matchEvent(Event.class, StateData.class,
(event, stateData) ->
stay().using(new StateData())));
when(State.Active,
matchEvent(Event.class, StateData.class,
(event, stateData) -> goTo(State.Idle).using(stateData.mutate())));
.......
public class StateData{
public StateData mutate(){
//mutate myself
return this;
}
Is it safe to mutate the data this way? I'm uncertain since I saw that
"akka.actor.AbstractFSM.onTransition(PartialFunction<Tuple2<BatchingState,
BatchingState>, BoxedUnit>)" allows you to access both the current stateData
and the nextStateData.
Any help would be much appreciated. Thanks and have a great day.
--
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>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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