Classin

A fork of rxi's tiny class module for Lua. Attempts to stay simple and provide decent performance by avoiding unnecessary over-abstraction.

Added features:

• :implement() no longer restricted to just functions, copies static fields as well
• EmmyLua annotations
• Added optional class name arg to :extend

Usage

The module should be dropped in to an existing project and required by:

Object = require "classic"

The module returns the object base class which can be extended to create any additional classes.

Creating a new class

Point = Object:extend('Point') -- optional name

function Point:new(x, y)
  self.x = x or 0
  self.y = y or 0
end

Creating a new object

local p = Point(10, 20)

Extending an existing class

Rect = Point:extend()

function Rect:new(x, y, width, height)
  Rect.super.new(self, x, y)
  self.width = width or 0
  self.height = height or 0
end

Checking an object's type

local p = Point(10, 20)
print(p:is(Object)) -- true
print(p:is(Point)) -- true
print(p:is(Rect)) -- false 

Using static variables

Point = Object:extend()
Point.scale = 2

function Point:new(x, y)
  self.x = x or 0
  self.y = y or 0
end

function Point:getScaled()
  return self.x * Point.scale, self.y * Point.scale
end

Creating a metamethod

function Point:__tostring()
  return self.x .. ", " .. self.y
end

Using mixins

PairPrinter = Object:extend()
PairPrinter.limit = 1

function PairPrinter:printPairs()
  local i = 0
  for k, v in pairs(self) do
    i = i + 1
    print(k, v)
    if i >= self.limit then return end
  end
end


Point = Object:extend()
Point:implement(PairPrinter)

function Point:new(x, y)
  self.x = x or 0
  self.y = y or 0
end


local p = Point()
p:printPairs() -- only prints one pair

License

This module is free software; you can redistribute it and/or modify it under the terms of the MIT license. See LICENSE for details.