Lua Stateful OOP mixin to be used with middleclass

• Classes gain the capacity of creating “states”
• States can override instance methods and create new ones
• States are inherited by subclasses
• States are stackable – the state on the top of the stack is the most prioritary
• There are callback functions invoked automatically when a state is entered, exited, pushed, popped …

What follows is a basic example:

require 'middleclass'
Stateful = require 'stateful'

local Enemy = class('Enemy')
Enemy:include(Stateful)

function Enemy:initialize(health)
  self.health = health
end

function Enemy:speak()
  return 'My health is' .. tostring(self.health)
end

local Immortal = Enemy:addState('Immortal')

-- overriden function
function Immortal:speak()
  return 'I am UNBREAKABLE!!'
end

-- added function
function Immortal:die()
  return 'I can not die now!'
end

local peter = Enemy:new(10)

peter:speak() -- My health is 10
peter:gotoState('Immortal')
peter:speak() -- I am UNBREAKABLE!!
peter:die() -- I can not die now!
peter:gotoState(nil)
peter:speak() -- My health is 10

First, make sure that you have downloaded and installed middleclass

Just copy the stateful.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:

require 'middleclass'
local Stateful = require 'stateful'

The package.path variable must be configured so that the folder in which stateful.lua is copied is available, of course.

Please make sure that you read the license, too (for your convenience it’s now included at the beginning of the middleclass.lua file).

This project uses telescope for its specs. If you want to run the specs, you will have to install telescope first. Then just execute the following from the root inspect folder:

tsc -f spec/*.lua