[Boost-users] Re: [boost::fsm] Accessing most recently posted event

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2005-05-03 08:11:19

Hi Marcin

> 	Is there a way that an event triggered on entry to a state can
> access the event that caused that state to be entered?

No, not currently. I was thinking about providing something like that but 
postponed it because I've never had the need. Neither have I revceived any 
other requests in that direction.

> 	I'm thinking of adding a line to the process_event method in a
> wrapper class derived from state_machine that stores the event object
> received as a way of doing this.

That works only as long as you don't post any events. I order to catch those 
events as well you'd need to do the same for state_machine::post_event, which 
is not part of the documented interface. I don't currently see a proper way 
how users can implement this themselves (save of changing the library code), 
if they want to be able to post events.
I think the best way is to add the following member function to the 
simple_state interface:

const event_base * current_event() const

If the state entry was triggered by an event, current_event() returns a 
pointer to the event that triggered the transition. Otherwise, it returns 0 
(e.g. the state was entered as a result of calling state_machine::initiate(). 
We could also name this triggering_event()...

Thoughts?

Regards,

--
Andreas Huber
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