Re: [Boost-users] [statechart] Unexpected events

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2006-02-22 19:34:54

David Greene wrote:
> I had assumed that if a state_machine definition did not mention any
> reaction for a particular event in a particular state, occurrence
> of that event in that state would be flagged as a runtime error.
>
> It appears that instead, the event is simply dropped.

This is the behavior mandated by the UML standard.

> Can this behavior be changed?  It would be tremendously helpful
> for debugging purposes.  Adding an error state and a bunch of
> transitions into it seems like overkill, especially if the
> cross product between states and events is large but the "in-
> and out-degree" of states is small.

[untested code]

struct EvUnconsumedEvent() : sc::event<EvUnconsumedEvent> {};

// Add the following member to your state_machine
// subtype (see reference):
void unconsumed_event( const sc::event_base & )
{
  post_event( new EvUnconsumedEvent() );
}

Your machine has two outermost states, e.g. Normal and 
UnconsumedEventError and a transition triggered by EvUnconsumedEvent 
leading from Normal to UnconsumedEventError. Of course, Normal would 
then contain all the states you have now.

HTH & Regards,

-- 
Andreas Huber
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