lua 操作 C++的類 ；manipulate c++ class with lua

準備弄cocos2dx的lua，搗騰一下lua，留點印記給後面的童鞋參考。（俺也是半吊子，如果看官發現啥不妥的地方，請使勁噴。我全接受）

1、版本：這是個坑。

首先 pil （programming in lua）國人（似乎是風雲大大）翻譯的版本是5.0 有點低了。

cocos2dx 2.15用的是lua 5.1 ，

最新的lua 是5.2 ，

最新的pil 3rd 也是5.2；

5.0 ；5.1; 5.2的函數變化了不少，剛接觸的時候會遇到即使是copy的代碼也跑錯的時候，就看你的code和lua環境是否一致吧。 網上大多程式碼範例都是5.0的，要稍加修改。

2、看書，lua不大，也不複雜。如果不是研究lua代碼實現的話，入門還是比較快的。

先把pil仔細翻幾遍，對文法都ok，然後再看 C 綁定的部分。這塊主要是metatable __index __newindex的幾個概念搞清晰。即可。

3、c，c++

這個其實就是用到上面（2）提到的技巧而已，本質上就是lua來通過glue代碼間接操作C++的class而已。

廢話不多說，趕著睡覺呢。。。。其實也說不清。看代碼吧。加了詳細的注釋了。

makefile

all:g++ -g3 -o cheneeout chenee.cpp  -lluaclean:rm -R *dSYM *out

chenee.lua

print "test lua access C++ Class"local a = Animal("dog")--local a = Animal.creat("dog")a:setAge(100)a:sound()print ("age is :" .. a:getAge())

chenee.cpp

////@chenee:this Demo showing how to manipulate the C++ class with LUA// LUA = the moon//#include <stdio.h>#include <string>#include <iostream>extern "C"{#include "lua.h"#include "lauxlib.h"#include "lualib.h"}//@chenee: to dump the lua stackstatic void stackDump(lua_State * L){inti;inttop = lua_gettop(L);/* depth of the stack */for (i = 1; i <= top; i++) {/* repeatforeachlevel */intt = lua_type(L, i);switch (t) {case LUA_TSTRING:{ /* strings */printf("'%s'", lua_tostring(L, i));break;}case LUA_TBOOLEAN:{ /* booleans */printf(lua_toboolean(L, i) ? "true" : "false");break;}case LUA_TNUMBER:{ /* numbers */printf("%g", lua_tonumber(L, i));break;}default:{/* other values */printf("%s", lua_typename(L, t));break;}}printf("  ");/* put a separator */}printf("\n");/* end the listing */}using namespace std;////@chenee: the class to be deal with;//class Animal{public:    Animal(std::string name):age(0){ this->name = name;};    void setAge(int age) { this->age = age;};    int getAge(){ return this->age;};    void sound(){ cout << " -- Animal name:   " << this->name << "  and it's Age:"<< this->age << endl;};private:    string name;    int age;};////@chenee: this class used as a tool to expose interfaces to lua//class LuaAnimal{    static const string className;    static const luaL_reg methods[];    static const luaL_reg methods_f[];    static int creat(lua_State *L){        string name (lua_tostring(L,1));        Animal *a = new Animal(name);        void **p = (void**)lua_newuserdata(L,sizeof(void*));        *p = a;      luaL_getmetatable(L, className.c_str());      lua_setmetatable(L, -2);      return 1;    }    static int gc_animal(lua_State *L) {        Animal *a = (Animal*)(*(void**)lua_touserdata(L,1));        delete a;//        cout << "Gc ....." << endl;        return 0;    }    static Animal* getAnimal(lua_State *L){        luaL_checktype(L,1,LUA_TUSERDATA);        void *ud = luaL_checkudata(L,1,className.c_str());        if(!ud){            luaL_typerror(L,1,className.c_str());        }        return *(Animal**)ud;    }    static int sound(lua_State *L){        Animal *a = getAnimal(L);        a->sound();        return 1;    }    static int setAge(lua_State *L){        Animal *a = getAnimal(L);        double age = luaL_checknumber(L, 2);        a->setAge(int(age));        return 0;    }    static int getAge(lua_State *L){        Animal *a = getAnimal(L);        int age = a->getAge();       lua_pushinteger(L, age);        return 1;    }public:    static void Register(lua_State* L) {        //1: new methods talbe for L to save functions        lua_newtable(L);        int methodtable = lua_gettop(L);        //2: new metatable for L to save "__index" "__newindex" "__gc" "__metatable" ...        luaL_newmetatable(L, className.c_str());        int metatable   = lua_gettop(L);        //3: metatable["__metatable"] = methodtable        lua_pushliteral(L, "__metatable");        lua_pushvalue(L, methodtable);        lua_settable(L, metatable);  // hide metatable from Lua getmetatable()        //4: metatable["__index"] = methodtable        lua_pushliteral(L, "__index");        lua_pushvalue(L, methodtable);        lua_settable(L, metatable);        //5: metatable["__gc"] = gc_animal         lua_pushliteral(L, "__gc");        lua_pushcfunction(L, gc_animal);        lua_settable(L, metatable);        lua_pop(L, 1);  // drop metatable        //6: for objct:        // name == 0 set object function to "methods"        //eg:Animal a = Animal("xx");        //a:func() in this "methods" table;        luaL_openlib(L, 0, methods, 0);  // fill methodtable        lua_pop(L, 1);  // drop methodtable        //7.1: for Class:        //name = "classname" , so this set Class function to "methods_f"        //eg:Animal a = Animal:creat("xx");        //Animal:creat() in this "methods_f" tables;//        luaL_openlib(L, className.c_str(), methods_f, 0);        //7.2: for Class:        //add global function "Classname", so we Animal() is a global function now        //Animal a = Animal("xx");        //function Animal()in lua will call "creat" in C++        lua_register(L, className.c_str(), creat);    }};const string LuaAnimal::className = "Animal";const luaL_reg LuaAnimal::methods[] = {    {"sound", LuaAnimal::sound},    {"setAge", LuaAnimal::setAge},    {"getAge", LuaAnimal::getAge},    {"__gc", LuaAnimal::gc_animal},    {NULL, NULL}};const luaL_reg LuaAnimal::methods_f[] = {    {"creat", LuaAnimal::creat},    {NULL, NULL}};int main(){lua_State      *L = luaL_newstate();    luaL_openlibs(L);//    LuaAnimal::Register(L);if (luaL_loadfile(L, "chenee.lua") || lua_pcall(L, 0, 0, 0)){        cout << "cannot run config. file:" << lua_tostring(L,-1) << endl;    }  lua_close(L);  return 0;}