Function pointer as parameter of a function to export in LUA ?

[Aurélien MAIGNAN]

Hi,

In my C++ code I have this fonction to export in lua using luabind :

inline void ScriptingApp::setCallBack(functionType func){_callbackFunc = func;}

doing this declaration :

luabind::class_<ScriptingApp>("ScriptingApp")
.def("setCallBack", &ScriptingApp::setCallBack)

The problem is that functionType is defined as a function pointer :

typedef const char * mstring;
typedef void (* functionType) (void, const int&, mstring);

And that doesn't compile.
I get this error :

Build Log 

 
 
Rebuild started: Project: ScriptingApp, Configuration: Debug|Win32

Command Lines 
 
 
Creating temporary file "f:\Silicon Worlds\TestPythonCpp\ScriptingApp\Debug\RSP00000626483936.rsp" with contents
[
/O2 /I "F:\Silicon Worlds\TestPythonCpp\PyOgre" /I "F:\Silicon Worlds\LuaBind\References\lua\include" /I "C:\Program Files\boost\boost_1_35_0" /I "F:\Silicon Worlds\LuaBind\References\luabind\include" /FD /EHsc /MDd /Fo"Debug\\" /Fd"Debug\vc80.pdb" /c /Z7 /TP ".\ScriptingApp.cpp"


".\Rocket.cpp"
]
Creating command line "cl.exe @"f:\Silicon Worlds\TestPythonCpp\ScriptingApp\Debug\RSP00000626483936.rsp" /nologo /errorReport:prompt"

Output Window 
 
 
Compiling...
ScriptingApp.cpp
C:\Program Files\Microsoft Visual Studio 8\VC\include\xutility(2282) : warning C4996: 'std::_Copy_opt': You have used a std:: construct that is not safe. See documentation on how to use the Safe Standard C++ Library

        C:\Program Files\Microsoft Visual Studio 8\VC\include\xutility(2270) : see declaration of 'std::_Copy_opt'
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/primitives.hpp(68) : see reference to function template instantiation '_OutIt std::copy(_InIt,_InIt,_OutIt)' being compiled

        with
        [
            _OutIt=char *,
            _InIt=const char *
        ]
F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/call.hpp(280) : error C2784: 'make_const_pointer::type luabind::detail::const_pointer_converter::apply(lua_State *,luabind::detail::by_const_pointer,int)' : could not deduce template argument for 'luabind::detail::by_const_pointer' from 'luabind::detail::by_pointer'

        with
        [
            T=void (int,const int &,mstring)
        ]
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/policy.hpp(755) : see declaration of 'luabind::detail::const_pointer_converter::apply'

        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/call.hpp(403) : see reference to function template instantiation 'int luabind::detail::returns::call(void (__thiscall ScriptingApp::* )(A0),WrappedClass *,lua_State *,Policies *const )' being compiled

        with
        [
            WrappedClass=ScriptingApp,
            Policies=luabind::detail::null_type,
            A0=functionType
        ]
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/class.hpp(210) : see reference to function template instantiation 'int luabind::detail::call(R (__thiscall ScriptingApp::* )(A0),WrappedClass *,lua_State *,const Policies *)' being compiled

        with
        [
            Class=ScriptingApp,
            Policies=luabind::detail::null_type,
            R=void,
            A0=functionType,
            WrappedClass=ScriptingApp
        ]

        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/class.hpp(209) : while compiling class template member function 'int luabind::detail::mem_fn_callback::operator ()(lua_State *) const'
        with

        [
            Fn=void (__thiscall ScriptingApp::* )(functionType),
            Class=ScriptingApp,
            Policies=luabind::detail::null_type
        ]
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/class.hpp(1218) : see reference to class template instantiation 'luabind::detail::mem_fn_callback' being compiled

        with
        [
            Fn=void (__thiscall ScriptingApp::* )(functionType),
            Class=ScriptingApp,
            Policies=luabind::detail::null_type
        ]
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/class.hpp(868) : see reference to function template instantiation 'luabind::class_ &luabind::class_::virtual_def(const char *,const F &,const Policies &,luabind::detail::null_type,boost::mpl::true_)' being compiled

        with
        [
            T=ScriptingApp,
            F=void (__thiscall ScriptingApp::* )(functionType),
            Policies=luabind::detail::null_type
        ]
        .\ScriptingApp.cpp(341) : see reference to function template instantiation 'luabind::class_ &luabind::class_::def(const char *,F)' being compiled

        with
        [
            T=ScriptingApp,
            F=void (__thiscall ScriptingApp::* )(functionType)
        ]
F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/call.hpp(282) : error C2784: 'void luabind::detail::const_pointer_converter::converter_postcall(lua_State *,luabind::detail::by_const_pointer,int)' : could not deduce template argument for 'luabind::detail::by_const_pointer' from 'luabind::detail::by_pointer'

        with
        [
            T=void (int,const int &,mstring)
        ]
        F:\Silicon Worlds\LuaBind\References\luabind\include\luabind/detail/policy.hpp(779) : see declaration of 'luabind::detail::const_pointer_converter::converter_postcall'

Rocket.cpp
Generating Code...
Results 

 
 
Build log was saved at "file://f:\Silicon Worlds\TestPythonCpp\ScriptingApp\Debug\BuildLog.htm"
ScriptingApp - 2 error(s), 1 warning(s)

I don't know if it is possible to use such function pointer as argument of a function to export in LUA ?
If not maybe trying to see what is possible using functor instead of function pointer might work ?

Thanks for any help,

Aurélien MAIGNAN

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[Enno Rehling]

Aurélien MAIGNAN wrote:

> Hi,
>
> In my C++ code I have this fonction to export in lua using luabind :
>
> inline void ScriptingApp::setCallBack(functionType func){_callbackFunc =
> func;}
>
> doing this declaration :
>
> luabind::class_<ScriptingApp>("ScriptingApp")
> .def("setCallBack", &ScriptingApp::setCallBack)
>
> The problem is that functionType is defined as a function pointer :

And the problem with that is that luabind cannot map this to one of the
integral types in Lua, and neither can it map it to one of your defined
classes.

Out of curiosity, and because it might help in understanding why you
want to this: How do you intend to call this function from your Lua
script? Where is the parameter coming from that you intend to pass?

If you want to pass a Lua function, that can be done by making the
parameter a luabind::object&, something like this:

static void
foo(const luabind::object& bar, int i, const char * str)
{
   try {
     bar(i, str);
   } catch (error& e) {
     // do your error handling here
   }
}

(this is untested; I just mixed together some bits from my own code)

Enno.
--
"Multiple exclamation marks [...] are a sure sign of a diseased mind."
                    - Terry Pratchett, "Eric" (http://tinyurl.com/evan)


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[Aurélien MAIGNAN]

Hi,
thanks for your reply.
My intend was to do something like that :
in C++ :
typedef void (*functionType) (void*, int) [sorry I wrote void instead of void* in my first mail]
class AClass {
  functionType _callbackFunc;
  void memberMethod(int);
  void memberMethodThatActLikeAListener(...);
  static void staticFunction(void* MyThis, int i)
  {
    AClass * Obj = reinterpret_cast<AClass*>(myThis);
    return Obj->memberMethod(i);
  };
  void setCallBack(functionType func);
  functionType getCallBack();
};
inline void AClass ::setCallBack(functionType func)
{_callbackFunc = func;}
inline functionType AClass ::getCallBack()
{return _callbackFunc;}
AClass ::memberMethodThatActLikeAListener(...)
{
  //do some stuff, and particularly :
  getCallBack()(this,id);
}

registering :

luabind::class_<AClass >("AClass ")
.def("setCallBack", &AClass ::setCallBack)
.def("staticFunction", &AClass ::staticFunction)

And in lua :

AClass a;
a:setCallBack(a:staticFunction);

This is what I wanted to do.
Up to now I manage to have another solution that act someway like this using what you suggested :
in C++ :
// the lua function to callback
luabind::object _callbackFunc;
void call_CallBack_Function(const int& id, mstring name);
void setCallBack(luabind::object func);
luabind::object getCallBack();

void AClass::call_CallBack_Function(const int& id, mstring name)
{
    if(_callbackFunc && luabind::type(_callbackFunc) == LUA_TFUNCTION)
    {
        luabind::call_function<void>(_callbackFunc, id, name, this);
    }
}


and in LUA :

--define the callback function
function doUpdatePos(id,name,self)
    print "\nI update the position NOW!\n"
    self:updatePos(id,name)
end

function initCallback()
    sas:setCallBack(doUpdatePos)
end

so instead of doing all the job in C++ in manage the callback process going from C+++ to lua and then going back from lua to C++.

Thanks,
Aurélien MAIGNAN

2008/6/23 Enno Rehling <enno.rehling@...>:

Aurélien MAIGNAN wrote:
> Hi,
>
> In my C++ code I have this fonction to export in lua using luabind :
>
> inline void ScriptingApp::setCallBack(functionType func){_callbackFunc =
> func;}
>
> doing this declaration :
>
> luabind::class_<ScriptingApp>("ScriptingApp")
> .def("setCallBack", &ScriptingApp::setCallBack)
>
> The problem is that functionType is defined as a function pointer :

And the problem with that is that luabind cannot map this to one of the
integral types in Lua, and neither can it map it to one of your defined
classes.

Out of curiosity, and because it might help in understanding why you
want to this: How do you intend to call this function from your Lua
script? Where is the parameter coming from that you intend to pass?

If you want to pass a Lua function, that can be done by making the
parameter a luabind::object&, something like this:

static void
foo(const luabind::object& bar, int i, const char * str)
{
  try {
    bar(i, str);
  } catch (error& e) {
    // do your error handling here
  }
}

(this is untested; I just mixed together some bits from my own code)

Enno.
--
"Multiple exclamation marks [...] are a sure sign of a diseased mind."
                   - Terry Pratchett, "Eric" (http://tinyurl.com/evan)


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