Re: [Boost-users] [msm] access to root fsm

18 Jul 2013

      On 16.07.2013 0:09, Christophe Henry wrote:

Hi,
...
Hi,
...
I have main fsm with two sub-levels.
The problem is, the sub-fsms need data which is held in root fsm, like:
Ah yes, a classical one, I really need to take care of this. I intend to
provide something variadic but I had no time to do it yet :(
...
...
...
3. Maybe, there is a easier way to communicate between sub-fsm's?

...
The easiest would be eiher:
- to call outer.get_state().data=...
- pass in the constructor of SubFsm a pointer to the outer.
Indeed it would, but I'm too lazy to manually iterate all sub-fsm's to 
do the same thing...

Finally, I took the second way.
...
As both still form a cycle, better would be a pointer to an interface,
or even better, to a type_erasure type representing the minimum needed
interface of the outer fsm. A boost::function would do too. I personally
use type_erasure.
in init_fsm struct I already have generic fsm type, how can type_erasure 
fit here?

test code:

#include <iostream>
#include 

#include 
#include 
#include 

using boost::msm::front::Row;

struct init {};
struct level1 {};
struct level2 {};

struct Level2_: public boost::msm::front::state_machine_def
{
	struct Empty : public boost::msm::front::state<> {};

	typedef boost::mpl::vector<Empty> initial_state;

	struct transition_table : public boost::mpl::vector<> {};

	int i_;	  // some data
};

typedef boost::msm::back::state_machine Level2;

struct Level1_: public boost::msm::front::state_machine_def
{
	struct Empty : public boost::msm::front::state<> {};

	typedef boost::mpl::vector<Empty> initial_state;

	struct transition_table : public boost::mpl::vector<
		Row < Empty, level2, Level2 >
	> {};

	int i_;
};

typedef boost::msm::back::state_machine Level1;

struct Root_: public boost::msm::front::state_machine_def
{
	struct Empty : public boost::msm::front::state<> {};

	struct Init : public boost::msm::front::state<> {};

	struct InitAction
	{
		template <typename RootT>
		struct init_fsm
		{
			init_fsm(RootT* root) : root_(root)
			{ }

			// sub-FSM
			template <typename T>
			typename boost::enable_if::type
				operator()(boost::msm::wrap<T>&) const
			{
				typedef typename T::stt stt;
				typedef typename boost::msm::back::generate_state_set<stt>::type 
all_states;

				auto& fsm(root_->get_state());			
				fsm.i_ = root_->i_ + 1;

				std::cout << typeid(T).name() << std::endl;

				boost::mpl::for_eachboost::mpl::placeholders::_1 >
					(init_fsm<T>(&fsm));
			}

			// normal states
			template <typename T>
			typename boost::disable_if::type
				operator()(boost::msm::wrap<T>&) const
			{ }

		protected:
			RootT* root_;
		};

		template 
		void operator()(EVT&, FSM& fsm, SourceState&, TargetState&) const
		{
			typedef typename FSM::stt stt;
			typedef typename  boost::msm::back::generate_state_set<stt>::type 
all_states;

			boost::mpl::for_eachboost::mpl::placeholders::_1 >
				(init_fsm<FSM>(&fsm));
		}
	};

	typedef boost::mpl::vector<Empty> initial_state;

	struct transition_table : public boost::mpl::vector<
		Row < Empty, init, Init, InitAction >,
		Row < Init, level1, Level1 >
	> {};

	int i_;	  // some data
};

typedef boost::msm::back::state_machine fsm_t;

int main()
{
	fsm_t fsm;
	fsm.i_ = 0;

	fsm.start();
	fsm.process_event(init());
	fsm.process_event(level1());
	fsm.process_event(level2());

	assert(fsm.i_ == 0);
	assert(fsm.get_state().i_ == 1);
	assert(fsm.get_state().get_state().i_ == 2);

	return 0;
};
...
HTH,
Christophe

Re: [Boost-users] [msm] access to root fsm

Sam Fisher