Классы в lua, или избавляемся от двоеточия

local MyClass = {} -- the table representing the class, which will double as the metatable for the instances
MyClass.__index = MyClass -- failed table lookups on the instances should fallback to the class table, to get methods

-- syntax equivalent to "MyClass.new = function..."
function MyClass.new(init)
  local self = setmetatable({}, MyClass)
  self.value = init
  return self
end

function MyClass.set_value(self, newval)
  self.value = newval
end

function MyClass.get_value(self)
  return self.value
end

local i = MyClass.new(5)
-- tbl:name(arg) is a shortcut for tbl.name(tbl, arg), except tbl is evaluated only once
print(i:get_value()) --> 5
i:set_value(6)
print(i:get_value()) --> 6

(взято с lua-users.org/wiki/ObjectOrientationTutorial)

createClass = function()
	local creator = {}
	creator.__private = {
		object_class = {},
	}
	
	creator.__oncall = function(class_creator)		
		-- Get the class definition so we can make needed variables private, static, etc.
		local this = class_creator()
		-- Initialize class from class definition
		__init = function()
			-- Init Public Static
			local class = {}
			if (type(this.__public_static) == "table") then
				class = this.__public_static
			end
			
			-- Init Object
			local thisClass = this
			local __constructor = function(...)
				local object = {}
				local this = class_creator()

				-- Init Public
				if (type(this.__public) == "table") then
					object = this.__public
				end

				-- Init static values of the class
				this.__public_static = thisClass.__public_static
				this.__private_static = thisClass.__private_static

				-- Call Constructor
				if (type(this.__construct) == "function") then
					this.__construct(...)
				end
				
				-- Returning constructed object
				return object
			end
			return {class = class, constructor = __constructor}
		end

		-- Creating class (returning constructor)
		local class_data = __init()
		local class = class_data.class
		local constructor = class_data.constructor

		-- Set class metatable (with setting constructor)
		local class_metatable = {
			__newindex = function(t, key, value)
				if type(t[key])=="nil" or type(t[key])=="function" then
					error("Attempt to redefine class")
				end
				rawset(t, key, value)
			end,
			__metatable = false,
			__call = function(t, ...)
				if type(t) == nil then
					error("Class object create failed!")
				end
				local obj = constructor(...)
				creator.__private.object_class[obj] = t
				local object_metatable = {
					__newindex = function(t, key, value)
						class = creator.__private.object_class[t]
						if type(class[key])~="nil" and type(class[key])~="function" then
							rawset(class, key, value)
							return
						end
						if type(t[key])~="nil" and type(t[key])~="function" then
							rawset(t, key, value)
							return
						end
						error("Attempt to redefine object")
					end,
					__index = t,
					__metatable = false,
				}
				setmetatable(obj, object_metatable)
				return obj
			end,
		}

		-- Setting class metatable to the class itself
		setmetatable(class, class_metatable)

		-- Returning resulting class
		return class
	end
	
	return creator.__oncall
end
createClass = createClass()