按值传递

我建议您将name作为setup和callHello的论据传递. 这解决了对象生存期的问题。

注意：从C++调用Lua函数，然后从Lua调用C++函数似乎效率很低。 你确定你的设计吗？ 你真的需要通过Lua进行这种额外的间接间接吗？

bindings.h

#pragma once
#include <iostream>
#include <string>
class Test {
public:
void callHello(std::string const &name, lua_State *L) {
lua_getglobal(L, "hello");
lua_pushstring(L, name.c_str());
if (lua_pcall(L, 1, 0, 0) != 0) {
std::cout << "failed to call hello functionn"
<< lua_tostring(L, -1) << 'n';
return;
}
}
};

test.cpp

#include <iostream>
#include <string>
#include <lua.hpp>
extern "C" int luaopen_my(lua_State *L);
class myLua {
public:
myLua(std::string const &name) {
lua_State *L = luaL_newstate();
luaL_openlibs(L);
luaopen_my(L);
const char *script = "function setup(name)n"
"    local test = my.Test()n"
"    test:callHello(name)n"
"endn"
"function hello(name)n"
"    print('hello is called by : ' .. name)"
"end";
if (luaL_dostring(L, script) != 0) {
std::cout << "failed to run lua scriptn"
<< lua_tostring(L, -1) << 'n';
lua_close(L);
return;
}
lua_getglobal(L, "setup");
lua_pushstring(L, name.c_str());
if (lua_pcall(L, 1, 0, 0) != 0) {
std::cout << "failed to call setup functionn"
<< lua_tostring(L, -1) << 'n';
lua_close(L);
return;
}
lua_close(L);
}
};
int main() {
myLua lua1("Apple");
myLua lua2("Orange");
}

通过轻用户数据传递

根据您的要求，您还可以将指向字符串的指针作为 lightuserdata 推送到注册表中，并在callHello函数中获取它。 由于各种原因，使用注册表很危险。 密钥可能会发生冲突，您必须绝对确定密钥未在其他地方使用。 指向C++数据的指针可能会悬而未决，Lua 不知道也不可能知道这一点，并且会很乐意为您提供一个无效的指针。 取消引用会导致难以调试的分段错误。

注意：我认为这是糟糕的设计，应该避免。 为了不必传递参数的方便而放弃内存安全听起来不是一个好的权衡。

bindings.h

#pragma once
#include <iostream>
#include <string>
class Test {
public:
void callHello(lua_State *L) {
// Fetch light userdata from the registry with key "name" and
// pray that it is there
lua_pushstring(L, "name");
lua_gettable(L, LUA_REGISTRYINDEX);
std::string name;
if (lua_islightuserdata(L, -1) == 1) {
name = *static_cast<std::string *>(lua_touserdata(L, -1));
lua_pop(L, 1);
} else {
lua_pushstring(L, "userdata corrupted or absent");
lua_error(L);
return;
}
// Call hello function with fetched name
lua_getglobal(L, "hello");
lua_pushstring(L, name.c_str());
if (lua_pcall(L, 1, 0, 0) != 0) {
std::cout << "failed to call hello functionn"
<< lua_tostring(L, -1) << 'n';
return;
}
}
};

test.cpp

#include <iostream>
#include <string>
#include <lua.hpp>
extern "C" int luaopen_my(lua_State *L);
class myLua {
public:
myLua(std::string name) {
lua_State *L = luaL_newstate();
luaL_openlibs(L);
luaopen_my(L);
const char *script = "function setup()n"
"    local test = my.Test()n"
"    test:callHello()n"
"endn"
"function hello(name)n"
"    print('hello is called by : ' .. name)"
"end";
if (luaL_dostring(L, script) != 0) {
std::cout << "failed to run lua scriptn"
<< lua_tostring(L, -1) << 'n';
lua_close(L);
return;
}
// Push light userdata into the registry with key "name"
lua_pushstring(L, "name");
lua_pushlightuserdata(L, static_cast<void *>(&name));
lua_settable(L, LUA_REGISTRYINDEX);
lua_getglobal(L, "setup");
if (lua_pcall(L, 0, 0, 0) != 0) {
std::cout << "failed to call setup functionn"
<< lua_tostring(L, -1) << 'n';
lua_close(L);
return;
}
lua_close(L);
}
};
int main() {
myLua lua1("Apple");
myLua lua2("Orange");
}

常见位

SWIG 接口文件不需要调整，无论哪种情况都保持不变。

my.i

%module my
%{
#include "bindings.h"
%}
%include <std_string.i>
%include <typemaps.i>
%typemap(default) (lua_State *L) 
{
$1 = L;
}
%include "bindings.h"

对于这两种情况，都可以进行编译和运行(例如(

$ swig -lua -c++ my.i
$ clang++ -Wall -Wextra -Wpedantic -I/usr/include/lua5.2/ my_wrap.cxx test.cpp -llua5.2
$ ./a.out 
hello is called by : Apple
hello is called by : Orange