Re: [boost] [MSM] Compile-time error using SubMachines and events that carries some data

Subject: Re: [boost] [MSM] Compile-time error using SubMachines and events that carries some data
From: Fernando Pelliccioni (fpelliccioni_at_[hidden])
Date: 2013-05-23 17:24:55

Thanks Takatoshi,

Seemed odd to me that MSM instantiate a State using a "wrong" Event.
I thought I was doing something wrong.

The enable_if solution works perfect. :)

Thanks and regards,
Fernando Pelliccioni

On Thu, May 23, 2013 at 3:53 PM, Takatoshi Kondo <redboltz_at_[hidden]> wrote:

> Hi Fernando,
>
> Boost.Msm instansiates on_entry member function with various events even if
> your transition never happen. Hence you can't assume that event handler's
> template palameta "Event" is always the event you set on your transition
> table.
> IIUC, this is a MSM spacification.
>
> To solve this problem, you can use SFINAE as follows:
>
>             struct StaringGame : public msm::front::state<>
>             {
>                 template <typename Event, typename FSM>
>                 void on_entry(Event const& event, FSM& fsm, typename
> boost::
> enable_if<boost::is_same<Event, character_selected> >::type* = 0 )
>                 {
>                     std::cout << "entering: StaringGame" << std::endl;
>                     std::cout << "event.element(): " << event.element() <<
> std::endl;
>                     std::cout << "event typeid: " << typeid(event).name()
>  << std::endl;
>                 }
>                 template <typename Event, typename FSM>
>                 void on_entry(Event const& event, FSM& fsm, typename
> boost::
> disable_if<boost::is_same<Event, character_selected> >::type* = 0 )
>                 {
>                 }
>             };
>
>             struct StartTurn: public msm::front::state<>
>             {
>                 template <typename Event, typename FSM>
>                 void on_entry(Event const& event, FSM& fsm, typename
> boost::
> enable_if<boost::is_same<Event, character_selected> >::type* = 0 )
>                 {
>                     std::cout << "entering: StartTurn" << std::endl;
>                     std::cout << "event.element(): " << event.element() <<
> std::endl;
>                     std::cout << "event typeid: " << typeid(event).name()
>  << std::endl;
>                 }
>                 template <typename Event, typename FSM>
>                 void on_entry(Event const& event, FSM& fsm, typename
> boost::
> disable_if<boost::is_same<Event, character_selected> >::type* = 0 )
>                 {
>                 }
>             };
>
> Could you try it?
>
> Takatoshi Kondo
>
>
>
> On Thu, May 23, 2013 at 11:05 AM, Fernando Pelliccioni <
> fpelliccioni_at_[hidden]> wrote:
>
> > Hi,
> >
> > I have a Main State Machine (state_machine_) and two SubMachines.
> > I want to start the first SubMachine and when it finished I want to start
> > the second SubMachine.
> >
> > Here is the code.
> >
> > http://pastebin.com/sBdS1wvJ
> >
> > I have a compile-time error on some States of the second SubMachine.
> >
> > error: no member named 'element' in 'exit_introduction'
> >                     std::cout << "event.element(): " << event.element()
> <<
> > std::endl;
> >                                                         ~~~~~ ^
> >
> > This is on state "StaringGame" and according the Transition Table of
> > GameSM, only the event "character_selected" is used.
> > I don't know why is trying to use the event "exit_introduction".
> >
> > Is this a bug of MSM?
> > Am I doing something wrong?
> >
> > Thanks and regards,
> > Fernando Pelliccioni.
> >
> > _______________________________________________
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> >
>
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