Lua中模拟创建一个类(使用Lua中的table)

该代码实现了一个在Lua中进行深度拷贝的函数`clone`，以及创建类和处理继承的`class`函数。`is_instance_of`函数用于判断一个对象是否是另一类的实例或其子类。类的创建支持从其他类（包括原生C++对象）继承，并提供了构造函数和元表设置。

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---@des 数据深拷贝(递归)
local function _copy(object, lookup_table)
    if type(object) ~= "table" then
        return object
    elseif lookup_table[object] then
        return lookup_table[object]
    end
    local new_table = {}
    lookup_table[object] = new_table
    for key, value in pairs(object) do
        new_table[_copy(key, lookup_table)] = _copy(value, lookup_table)
    end
    return setmetatable(new_table, getmetatable(object))
end

function clone(object)
    local lookup_table = {}
    return _copy(object, lookup_table)
end

---@des 创建一个类并返回
function class(classname, super)
    local superType = type(super)
    local cls

    if superType ~= "function" and superType ~= "table" then
        superType = nil
        super = nil
    end

    if superType == "function" or (super and super.__ctype == 1) then
        -- inherited from native C++ Object
        cls = {}
        if superType == "table" then
            for k, v in pairs(super) do
                cls[k] = v
            end
            cls.__create = super.__create
            cls.super = super
        else
            cls.__create = super
        end

        cls.ctor = function()end
        cls.__cname = classname
        cls.__ctype = 1

        function cls.new(...)
            local instance = cls.__create(...)
            for k, v in pairs(cls) do
                instance[k] = v
            end
            instance.class = cls
            instance:ctor(...)
            return instance
        end
    else
        -- inherited from Lua Object
        if super then
            cls = clone(super)
            cls.super = super
        else
            cls = { ctor = function() end }
        end

        cls.__cname = classname
        cls.__ctype = 2 -- lua
        cls.__index = cls

        function cls.new(...)
            local instance = setmetatable({}, cls)
            instance.class = cls
            instance:ctor(...)
            return instance
        end 
    end
    return cls
end

---@param A any class|object
---@param B any class
---@return boolean 判断A是否是B的实例或子类
function is_instance_of(A, B)
    if not A or not B then
        return false
    end
    A = A.class or A
    while A do
        if A == B then
            return true
        end
        A = A.super
    end
    return false
end
```