[erlang-questions] FSM: How to wait the end of handle_info ?

dmitry kolesnikov <>
Wed May 9 16:24:38 CEST 2012


Hello,

You can send message out of handle_info to parent process when state
is changed. Parent process shall have a receive handle.

You can use gen_event to dispatch notification about a changed state.

IMHO, there is something wrong with design if you need to synchronize
main routine with async message from socket. It should be
asynchronous...

Best Regards,
Dmitry >-|-|-*>


On 9.5.2012, at 16.53, Arnaud Garcia <> wrote:

> Hello everybody,
>
> I have two files, main.erl which control a finite state machine (FSM) with a gen_fsm behavior.
> The FSM is also able to received incoming data from a socket for certain state (using the handle_info method).
>
> The question is how the main program can wait and know the next state after handle_info callback is done by the gen_fsm....
> because, according to the rawdata received the system move to another state and main.erl must know this new state to send specifics events....
>
> Maybe more easy to understand with a small illustration
>
> main.erl
>    {ok, FSMPid} = myfsm:start_link(...),
>     ok =  gen_fsm:sync_send_event(FSMPid, event1)
>                   % => will move the FSM to state_5 where we are waiting socket incoming data
>                   % these data will be handle by "handle_info({tcp, _Socket, RawData}, state_5, StateData)"
>                   % depending on the received socket rawdata, we will change the state of the FSM
>
>
>        => How can I wait handle_info has finished ?
>        => How can I get the state ?
>               (for this last question, I think I can just send a send_all_state(FSMPid, current_state) for example and return the StateName
>
>     program will continue like this:
>     case StateName of
>          state_13 -> send another event
>       ....
>
>
>
>
>
> thanks for help,
>
> Arnaud
>
>
>
>
>
>
>
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