Implementing "super()" for classes

[Aaron MacDonald <aaronjm@...>]

I have a lightweight object orientation module. It's centred around this "createClass" function:

    function createClass(base)
        local newClass = {} -- Contains class methods
        local classMeta = { __index = newClass }

        if base
        then
            setmetatable(newClass, { __index = base })
        end

        -- Object creation is assumed to be Objective C style.
        -- Classes are expected to have an "init" method for
        -- initializing its variables.
        --
        -- object = Class.new()
        -- object:init(data1, data2, ... dataN)

        function newClass.new()
            local instance = {}
            setmetatable(instance, classMeta) -- "instance" may access
                                              -- class methods
            return instance
        end

        return newClass
    end

I would define and use classes like this:

    MyClass = createClass()

    -- The "constructor"
    function MyClass:init(data)
        self.data = data
    end

    function MyClass:printData()
        print(self.data)
    end

    object = MyClass.new()
    object:init('Hello')
    object:printData()

My issue is that I am unsure how to implement a "super" construct for accessing an object's superclass methods.  Ideally I'd be able to do something like this:

    MySubclass = createClass(MyClass)

    function MySubclass:init(data, extraData)
        self:super():init(data)
        self.extraData = extraData
    end

    function MySubclass:printData()
        self:super():printData()
        print(self.extraData)
    end

"self:super()" would, I assume, return a table with the object's data but with the functions of the superclass.  Could this be accomplished by making a copy of the object table and setting its metatable to the base class table?