myluaootest.lua

–1. 基本原理

local Cal = {}

function Cal:New(o)
	o = o or {}
	setmetatable(o, self)
	self.__index = self
	return o
end

function Cal:Add(a, b)
	print("Cal Add")
	return a + b
end

local SubCal = Cal:New()

function SubCal:Add(a, b)
	print("SubCal Add")
	return a + b + 10
end

–2. 雲風大大的優雅實現

https://blog.codingnow.com/cloud/LuaOO

local _class = {}

local function class(super)
	local class_type = {}
	class_type.ctor = false
	class_type.super = super
	class_type.new = function ( ... )
		local obj = {}
		do
			local create
			create = function (c, ... )
				if c.super then	
					create(c.super, ...)
				end

				if c.ctor then
					c.ctor(obj, ...)
				end
			end

			create(class_type, ...)
		end

		setmetatable(obj, {__index=_class[class_type]})

		return obj
	end

	local vtbl = {}
	_class[class_type] = vtbl

	setmetatable(class_type, {__newindex=function (t, k, v)
		vtbl[k] = v
	end})

	if super then
		setmetatable(vtbl, {__index=function (t, k)
			local ret = _class[super][k]
			vtbl[k] = ret
			return ret
		end})
	end

	return class_type
end

local A = class()

function A:ctor(x)
	print("A ctor", x)
	self.x = x
end

function A:print_x()
	print("A print_x", self.x)
end

function A:hello()
	print("A hello base_type")
end

local B = class(A)

function B:ctor(x)
	print("B ctor", x)
	self.x = x + 1
end

function B:hello()
	print("B hello base_type")
end
 

local test = {}
function test:main()
--1
	local a = SubCal:New()
	print(a:Add(1, 2))

--2
	local a = A.new(1)
	a:print_x()
	a:hello()

	local b = B.new(10)
	b:print_x()
	b:hello()
end

return test

--[[ 輸出結果
SubCal Add
13
A ctor	1
A print_x	1
A hello base_type
A ctor	10
B ctor	10
A print_x	11
B hello base_type
]]