Re: [statechart] Substates in dll

So taking the TuTest code as an starting point, here's what I would like
to
be able to do:

- Put TuTest.cpp and TuTest.hpp in a dll, TuTest.dll, called by the main
program. Keep the initial transition in the cpp file, as in the test code.
- Make the Initial state react to EvX by transitioning to a new state,
call
it MyState, defined in MyState.dll. MyState, in turn, would have its own
internal transitions and states, which it hides from clients by putting
them
in its own cpp files.

Ok.

In your reply you had said that the state dll, MyState.dll in this case,
won't have a link-time dependency on the state machine; it need only
include
its header. This would be true if the state machine were implemented
entirely in the header. However, the header won't be enough if its initial
transition is hidden in a cpp file; the state would need to link with the
state machine.

Right, my bad. After some reflection, it seems that your assessment is correct. You simply cannot push only some states of a state machine into dlls without introducing a circular dependency between binaries. However, it seems you can circumvent this relatively easily, as follows (UNTESTED):

*** MyStatechartBase.hpp (included from cpps compiled into both dlls) ***

// Depending on your platform, types/functions in this header might need
// to be properly exported/imported

// ...

struct EvWhatever : sc::event< EvWhatever > {};

struct State1;
struct MyStatechartBase : sc::state_machine< MyStatechartBase, State1 >
{
 virtual sc::result react( State1 & state1, const EvWhatever & ev ) = 0;
};

struct State1 : sc::simple_state< State1, MyStatechartBase >
{
 typedef sc::custom_reaction< EvWhatever > reactions;

 sc::result react( const EvWhatever & ev )
 {
  return outermost_context().react( this, ev );
 }
};

*** MyStatechartBase.cpp (compiled into MyStatechartBase.dll) ***

#include "MyStatechartBase.hpp"
// ...

*** MyStatechart.cpp (compiled into MyStatechart.dll) ***

// This might have to be split into hpp/cpp

#include "MyStatechartBase.hpp"
// ...

struct State2 : sc::simple_state< State2, MyStatechartBase > {};

struct MyStatechart : MyStatechartBase
{
 virtual sc::result react( State1 & state1, const EvWhatever & ev )
 {
  return state1.transit< State2 >();
 }
};

Of course, this has two (IMO minor) problems:
1) You cannot hide State1, it must be publicly visible
2) You have to subclass the state machine

It seems this should do pretty much what you want? If not, please let me know.

Regards,

--
Andreas Huber

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