Object

Very straight-forward OOP Library for Lua focused on simplicity and speed.

Overview

local object = require "object"

-- create a new prototype

Shape = object.prototype(function()
  width, height = 0, 0
  function constructor(self, width, height)
    self.width, self.height = width, height
  end
end)

-- inheritance

Square = object.prototype(Shape, function()
  function constructor(self, size)
    super.constructor(self, size, size)
  end
end)

-- creating objects

local rect1 = Shape(32, 16)
local square1 = object.create(Square, 16)

Usage

object.prototype([super,] defn)

Function used to create a new prototype, it returns a table containing all the variables defined in the defn function. It supports two parameters, a super prototype and a defining function, the super parameter is optional, the defn function is not.

When defining a new prototype all variable declarations made inside the defn function are not treated as global variables but rather as variables belonging to the future prototype table. Local variables will belong exclusively to the prototype table and will not be passed on to future objects, although they can still reference them (in a way local variables can be seen as static variables).

There are three special keywords to use inside the defn function: self, super and constructor.

The self keyword references the future prototype table itself.

local object = require "object"

Vector = object.prototype(function()
  x = 0       
  self.y = 0  -- same as the one before 
end)

The super keyword references a prototype table from which the new one will inherit its variables. When redefining a function already present in the super prototype you can use the super keyword to reference that prototype.

local object = require "object"

Shape = object.prototype(function()
  width, height = 0, 0
  function constructor(self, width, height)
    self.width, self.height = width, height
  end
end)

Square = object.prototype(Shape, function()
  function constructor(self, size)
    super.constructor(self, size, size)
  end
end)

And the constructor keyword can only be used to define a function that'll be called when a new object is created from the prototype table.

local object = require "object"

Vector = object.prototype(function()
  x, y = 0, 0
  function constructor(self, x, y)
    self.x, self.y = x, y
  end
end)

local vector1 = Vector(32, 32)
print(vector1.x, vector1.y)   --  32,   32

object.create(prototype, ...)

This function is used to create a new object from an existing prototype.

Alternatively you can call the prototype variable itself as a function to create a new object from it.

local object = require "object"

Vector = object.prototype(function()
  x, y = 0, 0
  function constructor(self, x, y)
    self.x, self.y = x, y
  end
end)

local vector1 = object.create(Vector, 128, 128)
local vector2 = Vector(32, 32)                    -- same as the one before