luaclass.lua

-- A stupid way to implement classes.
-- Don't do this.
local classMeta = {}
function classMeta:__call(...)
    local obj = setmetatable({}, self)
    obj:new(...)
    return obj
end

function classMeta:__tostring()
    return self.__name
end

function buildClass(body, name)
    for k,v in pairs(classMeta) do
        body[k] = v
    end
    body.__name = name
    body.__index = body
    setmetatable(body, body)
    _G[name] = body
end

function class(name)
    return function (arg)
        if type(arg) == "string" then
            return function(body)
                for k,v in pairs(_G[arg]) do
                    if body[k] == nil then
                        body[k] = v
                    end
                end
                buildClass(body, name)
            end
        elseif type(arg) == "table" then
            buildClass(arg, name)
        end
    end
end


class "Rectangle" {
    width = nil,
    height = nil,
    new = function(self, width, height)
        self.width = width
        self.height = height
    end,
    getArea = function(self)
        return self.width * self.height
    end
}

class "Square" "Rectangle" {
    new = function(self, side)
        self.width = side
        self.height = side
    end
}

local rec1 = Rectangle(2, 2)
local rec2 = Rectangle(2, 3)
print(rec1:getArea(), rec2:getArea())
print(Square(3):getArea())