[Old] Joining LUA to C++ Example

This information is from my old website and may no longer be relevant

This example demonstrates how to join LUA to C++ classes with very little coding.

tolua++ is an extended version of tolua. tolua is a tool which makes it easier to combine LUA and C/C++. It generates binding C/C++ code. tolua++ offers additional features and is designed for C++

You can download toLua++ from https://github.com/LuaDist/toluapp

And the source code for this example can be downloaded here

Genereating tolua source files

Type the following in the command prompt. You can prefix the source files with anything you like. My preference is to use the prefix “tolua_”.

tolua++ -o tolua_Player.cpp -H tolua_Player.h -n Player Player.pkg

The pkg file tells toLua++ what functions to make available to LUA.

When I run the exe I get the following output:

LUA: Player's health is 4
C++: Player's health is 4 - Now setting it to 6
C++: Player's health is now 6
LUA: Player's health is 6 - Now setting it to 11
LUA: Player's health is now 11

Code

// main.cpp
#include <iostream>
#include <string>
using namespace std;

#include <tolua++.h>
#include <lua.hpp>
#include <lualib.h>
#include <lauxlib.h>

#include "Player.h"
#include "tolua_Player.h"

int main()
{
    //
    // Perform initalization. TODO: Add error checking for tolua?
    //
    lua_State *L = lua_open();

    if (NULL == L) {
        cout << "Error Initializing lua\n";
        return -1;
    }

    luaL_openlibs(L);   // initalize all lua standard library functions
    tolua_open(L);          // initalize tolua
    tolua_Player_open(L);   // make Player class accessible from LUA

    //
    //  Run lua script to create player. This could also have been done using luaL_dostring().
    //
    luaL_dofile(L, "loadplayer.lua");

    //
    // Get the player object from lua
    //
    lua_getglobal(L, "player");
    Player* player = (Player*)tolua_tousertype(L, -1, 0);

    //
    // Display health and change value
    //
    cout << "\nC++: Player's health is " << player->getHealth() << " - Now setting it to 6";
    player->setHealth(6);
    cout << "\nC++: Player's health is now " << player->getHealth() << "\n";

    //
    // The player object in LUA should now be updated. This code could also be put inside a lua script.
    //
    luaL_dostring(L, "io.write(\"LUA: Player's health is \"..player:getHealth()..\" - Now setting it to 11\")");
    luaL_dostring(L, "player:setHealth(11)");
    cout << endl;
    luaL_dostring(L, "io.write(\"LUA: Player's health is now \"..player:getHealth())");

    //
    // Perform cleanup.
    //
    lua_close(L);
    return 0;
}

// Player.h
#ifndef PLAYER_H
#define PLAYER_H

class Player {
    private:
        int health;
    public:
        Player();
        ~Player();
        void setHealth(int _health);
        int getHealth();
};

#endif // PLAYER_H

// Player.cpp
#include "Player.h"

Player::Player()
{
    health = 0;
}

Player::~Player()
{

}

void Player::setHealth(int _health)
{
    health = _health;
}

int Player::getHealth()
{
    return health;
}

// Player.pkg
$#include "Player.h"

class Player {
    Player();
    ~Player();
    void setHealth(int _health);
    int getHealth();
};

-- loadplayer.lua
-- Create new Player object and set health
player = Player:new()
player:setHealth(4)

-- Display players health
io.write("LUA: Player's health is "..player:getHealth());