cocos2dx-lua class语法糖要注意了

function class(classname, super)
    local superType = type(super)
    local cls

    --如果父类既不是函数也不是table则说明父类为空
    if superType ~= "function" and superType ~= "table" then
        superType = nil
        super = nil
    end

    --如果父类的类型是函数或者是C对象
    if superType == "function" or (super and super.__ctype == 1) then
        -- inherited from native C++ Object
        cls = {}

        --如果父类是表则复制成员并且设置这个类的继承信息
        --如果是函数类型则设置构造方法并且设置ctor函数
        if superType == "table" then
            -- copy fields from super
            for k,v in pairs(super) do cls[k] = v end
            cls.__create = super.__create
            cls.super    = super
        else
            cls.__create = super
            cls.ctor = function() end
        end

        --设置类型的名称
        cls.__cname = classname
        cls.__ctype = 1

        --定义该类型的创建实例的函数为基类的构造函数后复制到子类实例
        --并且调用子数的ctor方法
        function cls.new(...)
            local instance = cls.__create(...)
            -- copy fields from class to native object
            for k,v in pairs(cls) do instance[k] = v end
            instance.class = cls
            instance:ctor(...)
            return instance
        end

    else
        --如果是继承自普通的lua表,则设置一下原型，并且构造实例后也会调用ctor方法
        -- inherited from Lua Object
        if super then
            cls = {}
            setmetatable(cls, {__index = 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

local Base = class(‘Base‘)
Base.__index = Base

function Base:ctor(id)
    print(‘Base:ctor‘,id)
    self.id = id
end

local ExtBase = class(‘ExtBase‘,Base)
ExtBase.__index = ExtBase

function ExtBase:ctor(id)
    --Base:ctor(id)
    super(self,id)
    print(‘ExtBase:ctor‘,id)
end