Re: [boost] boost [msm] deferring event by base type.

Subject: Re: [boost] boost [msm] deferring event by base type.
From: Juraj Ivančić (juraj.ivancic_at_[hidden])
Date: 2010-06-25 06:59:15

On 25.6.2010 10:40, Richard Szabo wrote:

> I'm now using Row and Defer functor I have now an other problem whit the :
>
>      void defer_event(Event const&  e)
>      {
>          // to call this function, you need either a state with a
> deferred_events typedef
>          // or that the fsm provides the activate_deferred_events typedef
>          BOOST_MPL_ASSERT(( has_fsm_deferred_events<library_sm>  ));
>          execute_return (library_sm::*pf) (Event const&  evt)=
> &library_sm::process_event;
>          Event temp (e);
>          ::boost::function<execute_return ()>  f= ::boost::bind(pf, this,temp);
>          post_deferred_event(f);
>      }
>
> actually it tries to instantiate the base class ( Event temp (e); )
> but in my case the base class is an abstract class ->  compiler error;
> and after deferring I want to dispatch the original derived event not
> the copy constructed base class instance of the event.

You might try the following:

Instead of making your event class polymorphic, you add a shared pointer 
to polymorphic data. E.g.

struct deferred_event
{
     boost::shared_ptr<deferred_event_data_base> event_data;
};

This would solve both issues as you would have a single event to be
deferred, and it would be copyable but would still retain polymorphic
data needed to process event.

HTH