Re: C++ binding

[Sean Conner <sean@...>]

It was thus said that the Great Timothée VERROUIL once stated:
> 
> Thanks a lot :)
> so I have to implemente __index as a function.
> But how can I do that in C++ ???

  Same way you write the routines for the other metatable functions.  As a
function, __index (in Lua) will be called with two paramters, the first
being the table (or userdata) and the second being the key.  So, a
hypothetical function might look like (and sorry this is in C; I don't use
C++ but you should be able to translate this):

static int foolua___index(lua_State *L)
{
  foo_t *foo;
  
  foo = luaL_checkudata(L,1,FOOTYPE);

  /*------------------------------------------------
  ; okay, index is a string.  Check what the index is
  ; and handle appropriately, pushing the appropriate
  ; values onto the stack.
  ;--------------------------------------------------*/

  if (lua_type(L,2) == LUA_TSTRING)
  {
    
    const char *key;
    size_t      ksize;
    
    key = lua_tolstring(L,2,&ksize);
    if (strcmp(key,"myAttribute") == 0)
    {
      lua_pushnumber(L,foo->myAttribute);
      return 1;
    }
    if (strcmp(key,"myFunction") == 0)
    {
      lua_pushcfunction(L,foolua_myfunction);
      return 1;
    }
    /* and so on .. */
  }

  /*---------------------------------------------
  ; we've got a number as a key
  ;---------------------------------------------*/
  
  else if (lua_type(L,2) == LUA_TNUMBER)
  {
    
    int idx;
    
    idx = lua_tointeger(L,2);
    if (idx > foo->maxIndex)
    {
      lua_pushnil(L);
      return 1;
    }
    lua_pushnumber(L,foo->data[idx]);
    return 1;
  }

  /*--------------------------------------------------
  ; something else, like a LUA_TTABLE or LUA_TBOOLEAN
  ; was passed in as the key.  If these make sense, 
  ; handle them, otherwise, return nil.
  ;---------------------------------------------------*/
  
  lua_pushnil(L);
  return 1;
}

    
And when you initialize the metatable:

  lua_pushcfunction(L,foolua___index);
  lua_setfield(L,-2,"__index");
  
  -spc (Hope this helps)