batteries/oo.lua

--[[
	barebones oop basics
	supports basic inheritance and means you don't have to build/set your own metatable each time

	todo: collect some stats on classes/optional global class registry
]]

function class(inherits)
	local c = {}
	c.__mt = {__index = c}
	--handle single inheritence
	if type(inherits) == "table" and inherits.__mt then
		setmetatable(c, inherits.__mt)
	end
	--common class functions

	--internal initialisation
	--sets up an initialised object with a default value table
	--performing a super construction if necessary and assigning the right metatable
	function c:init(t, ...)
		if inherits then
			--super ctor, then overlay args table
			t = table.overlay(inherits:new(...), t)
		end
		--upgrade to this class and return
		return setmetatable(t, self.__mt)
	end

	--constructor
	--generally to be overridden
	function c:new()
		return self:init({})
	end

	--get the inherited class for super calls if/as needed
	--allows overrides that still refer to superclass behaviour
	function c:super()
		return inherits
	end

	--done
	return c
end