从 Lua 在活动程序中调用 C++ 函数

I'm not sure if my question makes any sense, but I certainly know it is near impossible to get the results from Google. Firstly, what I do not want. I don't want to call some function that prints "hello world" or adds two numbers together, I want to load a Lua script from a C++ program, but allow the script to modify variables of the C++ program, using functions. For example, imagine I have a C++ program like this:

class Foo
{
    private:
        int number = 0;

    public:
        void setNumber(const int& newNumber) {number = newNumber;}
}

int main()
{
    Foo foo;

    //Load and execute Lua script, with foo object

    return 0;
}

我如何允许 Lua 脚本执行 foo.setNumber()(最好没有 foo.)?这可能是一个很简单的问题，但是如上所述，几乎所有关于谷歌的信息当搜索Call C++ Function from Lua"时假设没有程序，只有一个 .cpp/hpp 文件，其中包含一些您想要调用的函数.