metaclass

metaclass.lua

local Fabric = {}
Fabric.__metatable = {}
setmetatable(Fabric, Fabric.__metatable)

local Class = {}
Class.__metatable = {}
setmetatable(Class, Class.__metatable)

function Class.__metatable:__call(classname)
	local mt = {
		__name  = classname,
		__index = Class,
		__call  = Class.instance_object,
	}
	return setmetatable({
		implements = {},
		expects    = {},
		abstract   = true,
		__metatable = mt,
	}, mt)
end

function Class:instance_object(...)
	local mt = self.__metatable
	self.__metatable = nil

	setmetatable(self, {
		__index = self.parent
	})

	local args = {}
	if select("#", ...) == 1 and type(...) == "table" then
		args = ...
	end

	local object = setmetatable(args, {
		__index = self,
		__name  = mt.__name,
	})

	if type(self.constructor) == 'function' then
		object = object:constructor(...) or object
	end
	return object
end

function Class:inherits(...)
	local numargs = select("#", ...)
	if numargs ~= 1 then
		error("Expected exactly 1 class to inherit", 2)
	end

	local parent = ...
	parent = Fabric[parent]

	if not parent then
		error(string.format("Parent class '%s' not found", ...), 2)
	end

	self.parent = parent
	return self
end

function Fabric.__metatable:__call(name)
	if Fabric[name] then
		error(string.format("Class %s is already exists", name), 2)
	end

	local class = Class(name)
	Fabric[name] = class
	Fabric[class] = class
	return class
end

return Fabric