A simple OOP library for Lua. It has inheritance, metamethods (operators), class variables and weak mixin support.
local class = require 'middleclass' local Fruit = class('Fruit') -- 'Fruit' is the class' name function Fruit:initialize(sweetness) self.sweetness = sweetness end Fruit.static.sweetness_threshold = 5 -- class variable (also admits methods) function Fruit:isSweet() return self.sweetness > Fruit.sweetness_threshold end local Lemon = class('Lemon', Fruit) -- subclassing function Lemon:initialize() Fruit.initialize(self, 1) -- invoking the superclass' initializer end local lemon = Lemon:new() print(lemon:isSweet()) -- false
See the github wiki page for examples & documentation.
Just copy the middleclass.lua file wherever you want it (for example on a lib/ folder). Then write this in any Lua file where you want to use it:
local class = require 'middleclass'
This project uses busted for its specs. If you want to run the specs, you will have to install it first. Then just execute the following:
cd /folder/where/the/spec/folder/is busted
Middleclass also comes with a small performance test suite. Just run the following command:
Middleclass is distributed under the MIT license.
Updating from 2.x
Middleclass used to expose several global variables on the main scope. It does not do that anymore.
class is now returned by
require 'middleclass', and it is not set globally. So you can do this:
local class = require 'middleclass' local MyClass = class('MyClass') -- works as before
Object is not a global variable any more. But you can get it from
local class = require 'middleclass' local Object = class.Object print(Object) -- prints 'class Object'
The public functions
includes have been replaced by
Prior to 3.x:
instanceOf(MyClass, obj) subclassOf(Object, aClass) includes(aMixin, aClass)
obj:isInstanceOf(MyClass) aClass:isSubclassOf(Object) aClass:includes(aMixin)
The 3.x code snippet will throw an error if
obj is not an object, or if
aClass is not a class (since they will not implement
If you are unsure of whether
aClass are an object or a class, you can use the methods in
Object. They are prepared to work with random types, not just classes and instances:
Object.isInstanceOf(obj, MyClass) Object.isSubclassOf(aClass, Object) Object.includes(aClass, aMixin)
Notice that the parameter order is not the same now as it was in 2.x. Also note the change in naming:
isInstanceOf instead of
isSubclassOf instead of