lua实现伪多态继承

通过lua的设置元表__index字段，巧妙的运用在无法索引到对象的key时会调用__index的机制，实现了伪多态、继承。
代码如下：

inheritance = {}
_classTotalTable = {}

function inheritance:class(father)
local classVo = {}
classVo.constructor = false --构造函数
classVo.father = father  --父类
classVo.new = function(...)
local obj = {}
setmetatable(obj,{__index = _classTotalTable[classVo]})
local create
create = function(c,...)
if c.father then
create(c.father,...)
end
if c.constructor then
c.constructor(obj,...)
end
end
create(classVo,...)
return obj
end

local virtualTable = {}

-- tip:当经过此继承代码return的对象增加成员变量时，放入虚表
_classTotalTable[classVo] = virtualTable
setmetatable(classVo,{__newindex =
function(table,key,value)
virtualTable[key] = value
end
})
-- tip:索引不到对应key调用__index
-- 索引虚表，父类有此值，给予子类
if father then
setmetatable(virtualTable,{__index =
function (table,key)
local ret = _classTotalTable[father][key]
virtualTable[key] = ret
return ret
end
})
end

return classVo
end

--使用事例
baseClass = inheritance:class()

function baseClass:constructor()
print("base:constructor")
end

function baseClass:wowo()
print("base:wowo")
end

sonClass = inheritance:class(baseClass)

function sonClass:constructor()
print ("son:constructor")
end

function sonClass:wowo()
print("son:wowo")
end

newson = sonClass:new() --base:constructor   --son:constructor

newson:wowo()   --son:wowo