Re: [Boost-users] [statechart] Passing parameters from event to State Local Storage

6 May 2010


      Christophe Bourez <boost@bourez.be> writes:
...
I need to maintain a parameter into the state local storage. This
parameter is initially contained in the event that causes the transition to
the target state. I give hereafter a small illustrative example.
typename sc = boost::statechart;
class EvTest : public sc::event<EvTest>
{
public:
    EvTest(std::size_t val) : value(val) {}
    std::size_t getValue() const { return this->value; }
private:
    std::size_t value;
};
class MyStateMachine;
class StSource;
class StTarget;
class StSource : public sc::simple_state<StSource, MyStateMachine>
{
public:
    typedef sc::custom_reaction<EvTest> reactions;
sc::result react(const EvTest &event)
    {
        // How to pass event.getValue() to the target state ?
        transit<StTarget>();
    }
};
class StTarget : public sc::simple_state<StTarget, MyStateMachine>
{
public:
    StTarget(std::size_t val) : val(value) {}
private:
    std::size_t value;
};
I have a patch using boost.fusion to allow this. It works this way:

class StSource : public sc::simple_state<StSource, MyStateMachine>
{
public:
    typedef sc::custom_reaction<EvTest> reactions;
    sc::result react(const EvTest &event)
    {
        // How to pass event.getValue() to the target state ?
        transit<StTarget>(event.value); // pass arguments to target
                                        // state constructor
    }
};

Does Boost have interest in this?
...
Thanks,
Christophe
Regards,
--
Felipe Magno de Almeida