Re: [Boost-users] [Statechart] Question regarding state_machine eventhandling

Subject: Re: [Boost-users] [Statechart] Question regarding state_machine eventhandling
From: Andreas Huber (ahd6974-spamboostorgtrap_at_[hidden])
Date: 2010-02-26 12:32:04

> That's good to know - I did not realize that. From the tutorial and the
> reference I had the impression that a separate thread would be needed for 
> every
> other state machine, and I also wanted to go the easy way first ;-)
> I'll give it a try; according to the reference all functionality I need 
> seem to
> be available.

Ok, let me know if you have any trouble. Async machines differ quite a bit 
from sync ones.

>> state_machine<>::post_event() is not intended to be called from code
>> "outside" of the machine, but only transition actions, which is why
>> post_event is documented as being protected. Unfortunately, it is public 
>> in
>> the code because it has to be called from other class templates and 
>> template
>> friend support was very spotty at the time this was implemented. Anyway, 
>> I
>> certainly could have done more to prevent calls from outside (e.g. with 
>> an
>> assert and/or better documentation). May I ask you to enter a ticket for
>> this?
> Sure, the ticket is opened.

Thanks.

> Regarding my other questions about the synchroneous state machine: is it 
> really
> intended that a new event is processed before other events already queued? 
> Of
> course this might be related to the post_event() issue above - if events 
> cannot
> be queued up from outside without being processed immediately, the queue 
> cannot
> contain any pending events. Right?

Correct, if post_event is only ever called from transition actions then the 
posted events are processed as the last step of process_event, so there 
cannot be any event ordering issues.

Regards,

Andreas