Module:Middleclass
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Middleclass is an object-oriented library for Lua, written by Enrique García Cota (kikito) and maintained at GitHub.
If you are familiar with Object Orientation in other languages (C++, Java, Ruby … ) then you will probably find this library easy to use.
For a quick look at how to use the library see below. For the full documentation, see the wiki page on GitHub.
Quick Example
local class = require('Module:Middleclass').class
Person = class('Person') --this is the same as class('Person', Object) or Object:subclass('Person')
function Person:initialize(name)
self.name = name
end
function Person:speak()
return 'Hi, I am ' .. self.name ..'.'
end
AgedPerson = class('AgedPerson', Person) -- or Person:subclass('AgedPerson')
AgedPerson.static.ADULT_AGE = 18 --this is a class variable
function AgedPerson:initialize(name, age)
Person.initialize(self, name) -- this calls the parent's constructor (Person.initialize) on self
self.age = age
end
function AgedPerson:speak()
local hi = Person.speak(self) -- "Hi, I am xx."
if self.age < AgedPerson.ADULT_AGE then -- accessing a class variable from an instance method
return hi .. '\nI am underaged.'
else
return hi .. '\nI am an adult.'
end
end
local p1 = AgedPerson:new('Billy the Kid', 13) -- this is equivalent to AgedPerson('Billy the Kid', 13) - the :new part is implicit
local p2 = AgedPerson:new('Luke Skywalker', 21)
mw.log(p1:speak())
mw.log(p2:speak())
Output:
Hi, I'm Billy the Kid. I am underaged. Hi, I'm Luke Skywalker. I am an adult.
Notes:
The standard way to do inheritance is class(‘A’, B). In addition to that, you can also do B:subclass(‘A’). Both expressions will return A (a subclass of B). A.super will return B.
When you call A:new(), only A:initialize() gets called – the constructor of B is not called by default. There is no super, instead you have to use an explicit self:
function A:initialize()
...
B.initialize(self, ...)
...
end
The same applies for non-constructor methods – there is no super keyword-like construction, so you must use explicit self calls.
local middleclass = {
_VERSION = 'middleclass v4.0.0',
_DESCRIPTION = 'Object Orientation for Lua',
_URL = 'https://github.com/kikito/middleclass',
_LICENSE = [[
MIT LICENSE
Copyright (c) 2011 Enrique García Cota
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
]]
}
local function _createIndexWrapper(aClass, f)
if f == nil then
return aClass.__instanceDict
else
return function(self, name)
local value = aClass.__instanceDict[name]
if value ~= nil then
return value
elseif type(f) == "function" then
return (f(self, name))
else
return f[name]
end
end
end
end
local function _propagateInstanceMethod(aClass, name, f)
f = name == "__index" and _createIndexWrapper(aClass, f) or f
aClass.__instanceDict[name] = f
for subclass in pairs(aClass.subclasses) do
if rawget(subclass.__declaredMethods, name) == nil then
_propagateInstanceMethod(subclass, name, f)
end
end
end
local function _declareInstanceMethod(aClass, name, f)
aClass.__declaredMethods[name] = f
if f == nil and aClass.super then
f = aClass.super.__instanceDict[name]
end
_propagateInstanceMethod(aClass, name, f)
end
local function _tostring(self) return "class " .. self.name end
local function _call(self, ...) return self:new(...) end
local function _createClass(name, super)
local dict = {}
dict.__index = dict
local aClass = { name = name, super = super, static = {},
__instanceDict = dict, __declaredMethods = {},
subclasses = setmetatable({}, {__mode='k'}) }
if super then
setmetatable(aClass.static, { __index = function(_,k) return rawget(dict,k) or super.static[k] end })
else
setmetatable(aClass.static, { __index = function(_,k) return rawget(dict,k) end })
end
setmetatable(aClass, { __index = aClass.static, __tostring = _tostring,
__call = _call, __newindex = _declareInstanceMethod })
return aClass
end
local function _includeMixin(aClass, mixin)
assert(type(mixin) == 'table', "mixin must be a table")
for name,method in pairs(mixin) do
if name ~= "included" and name ~= "static" then aClass[name] = method end
end
for name,method in pairs(mixin.static or {}) do
aClass.static[name] = method
end
if type(mixin.included)=="function" then mixin:included(aClass) end
return aClass
end
local DefaultMixin = {
__tostring = function(self) return "instance of " .. tostring(self.class) end,
initialize = function(self, ...) end,
isInstanceOf = function(self, aClass)
return type(self) == 'table' and
type(self.class) == 'table' and
type(aClass) == 'table' and
( aClass == self.class or
type(aClass.isSubclassOf) == 'function' and
self.class:isSubclassOf(aClass) )
end,
static = {
allocate = function(self)
assert(type(self) == 'table', "Make sure that you are using 'Class:allocate' instead of 'Class.allocate'")
return setmetatable({ class = self }, self.__instanceDict)
end,
new = function(self, ...)
assert(type(self) == 'table', "Make sure that you are using 'Class:new' instead of 'Class.new'")
local instance = self:allocate()
instance:initialize(...)
return instance
end,
subclass = function(self, name)
assert(type(self) == 'table', "Make sure that you are using 'Class:subclass' instead of 'Class.subclass'")
assert(type(name) == "string", "You must provide a name(string) for your class")
local subclass = _createClass(name, self)
for methodName, f in pairs(self.__instanceDict) do
_propagateInstanceMethod(subclass, methodName, f)
end
subclass.initialize = function(instance, ...) return self.initialize(instance, ...) end
self.subclasses[subclass] = true
self:subclassed(subclass)
return subclass
end,
subclassed = function(self, other) end,
isSubclassOf = function(self, other)
return type(other) == 'table' and
type(self) == 'table' and
type(self.super) == 'table' and
( self.super == other or
type(self.super.isSubclassOf) == 'function' and
self.super:isSubclassOf(other) )
end,
include = function(self, ...)
assert(type(self) == 'table', "Make sure you that you are using 'Class:include' instead of 'Class.include'")
for _,mixin in ipairs({...}) do _includeMixin(self, mixin) end
return self
end
}
}
function middleclass.class(name, super)
assert(type(name) == 'string', "A name (string) is needed for the new class")
return super and super:subclass(name) or _includeMixin(_createClass(name), DefaultMixin)
end
setmetatable(middleclass, { __call = function(_, ...) return middleclass.class(...) end })
return middleclass
