[Boost-users] [MSM] How to access event-attributes through a "kleene"-event?

Subject: [Boost-users] [MSM] How to access event-attributes through a "kleene"-event?
From: Deniz Bahadir (deniz.bahadir_at_[hidden])
Date: 2013-02-19 11:18:01

Hello everyone,

I am trying to use Boost.MSM with the eUML front-end and I must say: 
That is a pretty cool thing! :-)

However, I stumbled across some points that raised several questions, 
which I hoped someone of you could answer.
One of these points is the usage of the "kleene" event (with eUML). The 
questions that came to mind are the following:

1. Is there a way to access an attribute of an (original) event if the 
transition-table uses the "kleene" event?

2. If there is a way, can I access it directly from the guard or 
actions-list in the transition-table?

3. If there is not a way, is it planned to be implemented (if possible) 
and when?

For better understanding I insert here a simple example which explains 
what I am trying to do:

In my special case, all my events have an attribute "EventNo" which is a 
unique number for each event(-type). Now, I need a transition for the 
events with "EventNo" greater than a special number (e.g. 7). So I 
thought, I could do something like this:

// The attribute:
BOOST_MSM_EUML_DECLARE_ATTRIBUTE(int, EventNo)
BOOST_MSM_EUML_ATTRIBUTES((attributes_ << EventNo), EventNoAttr)
// All events that contain this attribute:
BOOST_MSM_EUML_EVENT_WITH_ATTRIBUTES(event1, EventNoAttr)
BOOST_MSM_EUML_EVENT_WITH_ATTRIBUTES(event2, EventNoAttr)
   /* ... */
BOOST_MSM_EUML_EVENT_WITH_ATTRIBUTES(eventN, EventNoAttr)

// Entry-action of FSM which initializes these event-numbers:
BOOST_MSM_EUML_ACTION(init_all_events)
{
   template <class Evt, class Fsm, class State>
   void operator()(Evt const&, Fsm&, State&)
   {
     event1.get_attribute(EventNo) = 1;
     event2.get_attribute(EventNo) = 2;
       /* ... */
     eventN.get_attribute(EventNo) = N;
   };
}

// Some states:
BOOST_MSM_EUML_STATE((), State1)
BOOST_MSM_EUML_STATE((), State2)

// The transition table which contains all the logic:
BOOST_MSM_EUML_TRANSITION_TABLE((
   State1 + kleene
            [event_(EventNo) > Int_<7>()]  // <-- Not working!
                   == State2,
   State1 + event1 == State3
   /* event2 to event7 are ignored! */
), stt)

// The FSM front-end and back-end:
BOOST_MSM_EUML_DECLARE_STATE_MACHINE((
   stt, init_ << init_all_events
), FsmFrontend;
typedef msm::back::state_machine<FsmFrontend> Fsm;

However, the expression "event_(EventNo)" in the transition-guard fails 
to compile with the following error:

error: no match for call to 
‘(boost::msm::front::euml::GetEvent_<EventNo_>) (const 
boost::msm::front::euml::kleene_&, boost::msm::back::state_machine< 
boost::msm::front::euml::func_state_machine<FsmFrontendtag, ...’

I read in the documentation of the Functor front-end that I should use 
boost::any::type() to access the original event in transition actions, 
but I do not really know how to go on with it. I am also not sure if 
this applies to the eUML front-end at all (especially in the 
transition-guard).

I hope someone can help me and answer these questions!?

Thanks in advance,

Deniz Bahadir