hump/class.lua

--[[
Copyright (c) 2010-2013 Matthias Richter

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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]]--

local function include_helper(to, from, seen)
	if from == nil then
		return to
	elseif type(from) ~= 'table' then
		return from
	elseif seen[from] then
		return seen[from]
	end

	seen[from] = to
	for k,v in pairs(from) do
		k = include_helper({}, k, seen) -- keys might also be tables
		if to[k] == nil then
			to[k] = include_helper({}, v, seen)
		end
	end
	return to
end

-- deeply copies `other' into `class'. keys in `other' that are already
-- defined in `class' are omitted
local function include(class, other)
	return include_helper(class, other, {})
end

-- returns a deep copy of `other'
local function clone(other)
	return setmetatable(include({}, other), getmetatable(other))
end

local function new(class)
	-- mixins
	local inc = class.__includes or {}
	if getmetatable(inc) then inc = {inc} end

	for _, other in ipairs(inc) do
		if type(other) == "string" then
			other = _G[other]
		end
		include(class, other)
	end

	-- class implementation
	class.__index = class
	class.init    = class.init    or class[1] or function() end
	class.include = class.include or include
	class.clone   = class.clone   or clone

	-- constructor call
	return setmetatable(class, {__call = function(c, ...)
		local o = setmetatable({}, c)
		o:init(...)
		return o
	end})
end

-- interface for cross class-system compatibility (see https://github.com/bartbes/Class-Commons).
if class_commons ~= false and not common then
	common = {}
	function common.class(name, prototype, parent)
		return new{__includes = {prototype, parent}}
	end
	function common.instance(class, ...)
		return class(...)
	end
end


-- the module
return setmetatable({new = new, include = include, clone = clone},
	{__call = function(_,...) return new(...) end})