Lua Classes!

This module lets you create javascript-like classes in lua!

You should have some understanding of javascript classes including: constructors, getters/setters, and statics to use this.

Installation

Your lua version needs getfenv() To install, copy the source code into a new lua file and name it "classes.lua" You require it by doing

require("classes")

and initialize it by doing

require("classes")(getfenv())

Creating a class

You can easily create a class by typing class 'class_name' {} Here is an example of using this to create a user.

require("classes")(getfenv())
class 'User' {
  constructor = function(first_name, last_name, age)
    this.first_name = first_name
    this.last_name = last_name
    this.age = age
  end,
  get 'full_name' {
    function()
      return this.first_name.." "..this.last_name
    end
  },
  set 'full_name' {
    function(t)
      this.first_name = t[1]
      this.last_name = t[2]
    end
  }
}

Using classes

Using our example from before, you can do this.

local John = new "User" ("John", "Smith", 29)
print(John.full_name) --> John Smith
John.full_name = {"John", "Doe")
print(John.full_name) --> John Doe

Getters and Setters

Getters

Getters allow you to define properties Here is an example:

class "User" {
  constructor = function(first_name, last_name, age)
    this.first_name = first_name
    this.last_name = last_name
    this.age = age
  end,
  get 'full_name' {
		function()
			return this.first_name.." "..this.last_name
		end
  }
}
local John = new "User" ("John", "Smith", 29)
print(John.full_name) -- "John Smith"

Setters

Setters allow you to run code when you change a property. Here is an example:

class "User" {
  constructor = function(first_name, last_name, age)
    this.first_name = first_name
    this.last_name = last_name
    this.age = age
  end,
  get 'age' {
		function()
			return this.age
		end
  },
  set 'age' {
	function(age)
		if age < this.age then
			return print(("Cannot set %s's age to something less than its current age"):format(this.first_name))
		else
			this.age = age
		end
	end
  }
}
local John = new "User" ("John", "Smith", 29)
print(John.age) --> 29
John.age = 100
print(John.age) --> 100
John.age = 99 --> Cannot set John's age to something less than its current age
print(John.age) --> 100

Prototype

You can add to methods and properties to classes using prototype Here is an example using the same class as above.

User.prototype.double_age = function()
  return this.age * 2
end
local John = new "User" ("John", "Smith", 29)
print(John.double_age) --> 58

Advanced

You can even make a function return a class! Example:

function MakeRectangle(length, width)
	return class {
		constructor = function()
			this.length = length
			this.width = width
		end,
		get 'area' {
			function()
				return this.length * this.width
			end
		},
		set 'area' {
			function(new_area)
				this.length = new_area/2
				this.width = new_area/2
			end
		}
	}
end
local MyRectangle = MakeRectangle(20, 40)
local Rect = new (MyRectangle)()
print(Rect.area) --> 800

Errors

Your code editor probably tells you that many things are undefined including 'class', 'new', 'get', 'set', 'static', 'this', and any names of the classes. To silence these errors, put this before you initialize this module:

class, new, get, set, static, this = nil, nil, nil, nil, nil, nil

Thats it! Its a pretty simple module.