class.lua's Introduction

class.lua

This repository provides a code snippet that allows you to write classes in the Lua scripting language, compatible with Lua 5.3.

Features

Constructor and destructor (construct and destruct methods)
Inheritance (Class(BaseClass), SubClass.super)
Getters and setters (getXxx and setXxx methods and use xxx as the virtual properties)
instanceOf function

Usage

Just load the class.lua file in your Lua runtime environment and a function named Class is available. If you prefer another name, or want to require the file and return the function instead of creating a new global, feel free to modify the source code.

-- load `Class` into the global environment
require('class')

-- create a new class, named `BaseClass`
local BaseClass = Class()

-- constructor function must be named `construct`
function BaseClass:construct(text)
  print('Constructing BaseClass:', self)
  self.text = text
end

-- if this instance is being garbage collected, this is called
function BaseClass:destruct()
  print('Destructing BaseClass:', self)
end

-- regular method
function BaseClass:sayIt()
  print(self.text)
end

-- setter method must have the form `setXxx`
function BaseClass:setFoobar(value)
  print('Set foobar to:', value)
end

-- getter method must have the form `getXxx`
function BaseClass:getFoobar()
  print('Get foobar')
  return 27
end

local instance = BaseClass('Welcome class.lua!')
instance:sayIt() -- call regular method
instance.text = 'modified' -- modify regular property
instance.foobar = 'setting' -- uses setFoobar()
print(instance.foobar) -- uses getFoobar()
print(Class.instanceOf(instance, BaseClass)) -- true
print(instance:instanceOf(BaseClass)) -- true


local SubClass = Class(BaseClass)

function SubClass:construct()
  SubClass.super.construct(self, 'lorem ipsum dolor')
  -- or: BaseClass.construct(self, 'lorem ipsum dolor')
end