Lua Inheritance

Animal.lua

Animal = { name="undefined",sound="no sound" }

function Animal:new (newname, newsound)
  local o = {name=newname,sound=newsound}
  setmetatable(o, self)
  self.__index = self
  return o
end

function Animal:toString()
  animalStr = string.format("%s says %s", self.name, self.sound)
  return animalStr
end

Cat.lua

require "Animal"

Cat = Animal:new()
function Cat:new (name, sound)
  setmetatable( {}, Cat )

  self.name = name
  self.sound = sound

  return self
end

function Cat:toString()
  animalStr = string.format("A cat called %s says %s!", self.name, self.sound)
  return animalStr
end

Dog.lua

require "Animal"

Dog = Animal:new()
function Dog:new (name, sound)
  setmetatable( {}, Dog )

  self.name = name
  self.sound = sound

  return self
end

function Dog:toString()
  animalStr = string.format("A dog called %s says %s", self.name, self.sound)
  return animalStr
end

Main.lua

require "Cat"
require "Dog"

fluffy = Cat:new("Fluffy", "Meow")
print(fluffy:toString())

snoppy = Dog:new("Snoppy", "Woof")
print(snoppy:toString())

animal = Animal:new("Generic Animal", "Noise")
print (animal:toString())

animal = Animal:new()
print (animal:toString())

fluffy = Cat:new()
print(fluffy:toString())