在 C++ 中快速创建 LUA 自定义数据类型（带元表）的对象的一种包装方法

main.cpp

#include <cstdio>
#include <string>
#include <iostream>

#include <lua/lua.hpp>

#define LUAAPI(name)                static int name(lua_State* L)

#define DECL_OBJECT(T)              class T

#define DECL_THIS                   auto& O = *__this__(L)

#define _BEG_OBJ_API_(N, T) \
                                    static T* __this__(lua_State* L)        {return static_cast<T*>(luaL_checkudata(L, 1, __name__()));}\
                                    static const char* const __name__()     { return "" #N "::" #T; }\
                                    static const wchar_t* const __namew__() { return L"" #N  L"::" #T; }\
                                    static const luaL_Reg* const __apis__() { static luaL_Reg s_apis[] = {

#define BEG_OBJ_API(N, T)           LUAAPI(__gc)\
                                    {\
                                        DECL_THIS;\
                                        O.~T();\
                                        return 0;\
                                    }\
                                    _BEG_OBJ_API_(N, T)\
                                    OBJAPI(__gc)

#define OBJAPI(name)                {#name, name},

#define END_OBJ_API()               {nullptr, nullptr} }; return s_apis; }

// ----------------------------------------------------------------------------

void SetObjectMetatable(lua_State* L, const char* name, const luaL_Reg* fns)
{
    if(luaL_getmetatable(L, name) == LUA_TNIL) {
        lua_pop(L, 1);
        luaL_newmetatable(L, name);
        luaL_setfuncs(L, fns, 0);
        lua_pushvalue(L, -1);
        lua_setfield(L, -2, "__index");
    }

    lua_setmetatable(L, -2);
}

template<typename T, typename... Args>
T* PushObject(lua_State* L, Args... args)
{
    void* m = lua_newuserdata(L, sizeof(T));

    auto p = new (m) T(std::forward<Args>(args)...);

    SetObjectMetatable(L, T::__name__(), T::__apis__());

    return p;
}

// ----------------------------------------------------------------------------

DECL_OBJECT(MyObject)
{
public:
    MyObject(int x, const std::string& s)
        : _x(x)
        , _s(s)
    {
        std::cout << __FUNCTION__
            << ": x: " << _x
            << ", s: " << _s
            << std::endl;
    }
    ~MyObject()
    {
        std::cout << __FUNCTION__ << std::endl;
    }

    BEG_OBJ_API(::, MyObject)
        OBJAPI(fun1)
        OBJAPI(fun2)
    END_OBJ_API()

protected:
    LUAAPI(fun1)
    {
        DECL_THIS;
        std::cout << __FUNCTION__ << ": " << O._x << std::endl;
        return 0;
    }

    LUAAPI(fun2)
    {
        DECL_THIS;
        return 0;
    }

private:
    int             _x;
    std::string     _s;
};

// ----------------------------------------------------------------------------

int main()
{
    lua_State* L;

    L = luaL_newstate();

    PushObject<MyObject>(L, 123, "str");
    lua_setglobal(L, "obj");
    
    luaL_dostring(L, R"(obj:fun1() obj = nil)");

    lua_close(L);

    return 0;
}