Binding class method to Lua

Question

If I have class

class Game {
    public:
        Game() { level = new Level(); }

    private:
        Level *level;
        lua_State *L;
}

Where the level class has member functions such as "addObject()", how can I use that instance of the level class to bind addObject into the lua state?

The lua file may contain:

addObject("Player", 100, 100)
addObject("Enemy", 200, 100)

So to clarify, the 'Game' class contains a class 'Level' to manage things like the objects + there movement etc... Then I want to call a lua script to load the current level, which will bind the instance of 'Level' in the 'Game' class so it can call addObject() from the lua code.

I believe this is possible via LuaBind however I'm not keen on the boost dependencies, I did come across https://stackoverflow.com/questions/32416388/how-to-register-member-function-to-lua-without-lua-bind-in-c however method 1 seems to reply on 'Game' being a singleton and on method 2 I failed to bind a member method, only a normal function. If all else fails I will revert to LuaBind with it's awful dependencies.

Answer 1

Use Luna for C++ object binding to Lua. It is essentially a single header file containing helper functions to bind a C++ class to Lua. The previous version also contains instructions as to how to get it working. The usage is very simple, but you have to write boilerplate code, a wrapper class for each of your classes you wish to bind.

Answer 2

Okay, you can do this using user data, simple as pushing a pointer of Level onto the stack using lua_pushlightuserdata. Then getting the user data off the stack when the get_object function is called:

Level *lvl = (Level*)lua_touserdata(L, 1);
lvl->addObject(...);

http://www.gamedev.net/page/resources/_/technical/game-programming/the-lua-tutorial-r2999