[Boost-users] [StateChart] Inheriting state

Subject: [Boost-users] [StateChart] Inheriting state
From: Igor R (boost.lists_at_[hidden])
Date: 2010-02-03 18:06:13

Hello,

I'd like to share some functionality between states belonging to
different (but similar) FSMs. I try to do this by taking out some part
of a state to a base class template:

template<class Derived, class Outer, class Inner>
struct ActiveBase : state<Derived, Outer, Inner>
{
  // this's probably not quite standard, but it should be fine with msvc
  ActiveBase(my_context ctx) : my_base(ctx)
  {}

  void f(const Event1 &)
  {}
};

struct Active;
struct FSM : asynchronous_state_machine<FSM, Active>
{
//...
};

struct Active : ActiveBase<Active, FSM, Disconnected>
{
  Active(my_context ctx) : ActiveBase(ctx)
  {}
  typedef mpl::list
  <
    sc::in_state_reaction<Event1, ActiveBase, &ActiveBase::f>
  > reactions;
};

However, this doesn't compile:

1>..\boost/statechart/state_machine.hpp(493) : error C2440: 'return' :
cannot convert from 'FSM' to 'ActiveBase<Derived,Outer,Inner> &'
1>        with
1>        [
1>            Derived=Active,
1>            Outer=FSM,
1>            Inner=boost::mpl::list<Disconnected>
1>        ]
1>        ../boost/statechart/simple_state.hpp(684) : see reference to
function template instantiation 'Context
&boost::statechart::state_machine<MostDerived,InitialState,Allocator,ExceptionTranslator>::context<OtherContext>(void)'
being compiled
1>        with
1>        [
1>            Context=ActiveBase<Active,FSM,boost::mpl::list<Disconnected>>,
1>            MostDerived=FSM,
1>            InitialState=Active,
1>            Allocator=std::allocator<void>,
1>            ExceptionTranslator=boost::statechart::null_exception_translator,
1>            OtherContext=ActiveBase<Active,FSM,boost::mpl::list<Disconnected>>
1>        ]
etc........

Of course, the above snippet is not the real code, and maybe I miss
the problem in some other place, but I just would like to know if the
above approach legitimate and *should* compile.

Thanks.