Re: Newbie: How to make static pointers avaiblabe in Lua script from C++

["Eric Chou" <ericchou.cpp@...>]

You can't use lunar::Register() to wrap the static member function. because,  each call to registered member function, actually call the Lunar::thunk() with upvalue, which needs a userdata setted metatable on the bottom of the stack. You can read Lunar source code for detail.

/** Lua test code

a = CCC:getInstance()  --CCC is a table, not userdata
a.print( "Hello" ) ;         -- a is lightuserdata, haven't been set metatable.

*/
so , above code has errors.


I have done this work as follow :)

Add this function to Lunar:
static void Lunar<T>::register_functions(lua_State *L)
{
            luaL_openlib(L, T::className, T::functions, 0);
            lua_pop(L, 1);
}

each class which has static member function you want to wrap add :
static luaL_reg functions[];

As you example, you can write:
luaL_reg CCC::functions[] = {
    { "getInstance", CCC::getInstance },
    {0, 0}
};

Then you can use lunar<CCC>::register_functions(pLuaState) to wrap static member function in CCC::functions array.

CCC::getInstance code:
int CCC::getInstance(lua_State* L )
{
  Lunar<CCC>::push( L, Instance() ) ;  // must use this method to push lightuser in order to set metatable .
  return 1 ;
}

Lua test code:
a = CCC:getInstance()   -- after call, a is a userdata already seted metatable
a:print( "Hello" )  -- must use ':', or a.print( a, "Hello" )


Maybe these above can help you.

On 2/27/06, Roland Strålberg <rstralberg@msn.com> wrote:

Hi
After have trying and reading and trying I still cant get following to work
(its a singleton)
I'm using Lunar.h. Sorry for this long post but I really need some starting
help.

class CCC
{
public:
  static CCC* Instance() ;
  void Print( const char* pText ) {  }

  CCC() {}
  ~CCC() {}
private:
  static CCC* m_pInstance ;

// Lua declaration
public:
static const char className[];
static Lunar<CCC>::RegType methods[];

CCC( lua_State* ) ;
int getInstance( lua_State* ) ;
int print( lua_State* ) ;
} ;

CCC* CCC::m_pInstance = 0 ;
CCC* CCC::Instance()
{
  if ( m_pInstance == 0 )
    m_pInstance = new CCC ;
  return m_pInstance ;
}

// Lua implenation
const char CCC::className[] = "CCC" ;

Lunar<CCC>::RegType CCC::methods[] =
{
  { "getInstance", &CCC::getInstance },
  { "print", &CCC::print},
  { 0, 0 }
} ;

CCC::CCC( lua_State* L )
{
}

int CCC::getInstance(lua_State* L )
{
  lua_pushlightuserdata( L, Instance() ) ;
  return 1 ;
}

int CCC::print(lua_State* L )
{
const char* p = luaL_checkstring( L, -1 ) ;
Print( p ) ;
return 0 ;
}

// CCC is registered somewhere else with
// Lunar<CCC>::Register( pLuaState ) ;

/** Lua test code

a = CCC:getInstance()
a.print( "Hello" ) ;

*/

I can compile without errors
but when i run my program and executes the lua.file
loaded by luaL_loadfile( L, "test.lua" ), and then lua_pcall( L, 0,
LUA_MULTRET, 0 )
i get this error when a = CCC:getInstance() is executed in script

"calling 'getInstance' on bad self (CCC expected, got table)'"

I would be really thankful for any help.
Roland Strålberg

mailto:rstralberg@msn.com
http://www.rstralberg.com

-- 
Best Regards
Eric

Mailto: EricChou.Cpp@gmail.com
MSN:  storm_joe@hotmail.com