Re: Moving towards a class system package proposal

[PA <petite.abeille@...>]

On Jan 22, 2005, at 21:30, Mark Hamburg wrote:

> where objc_super is defined as "including the instance of the class 
> that is
> to receive the message and the superclass at which to start searching 
> for
> the method implementation".

Still waiting for my Lua book to show up... so feel free to slap me on 
the head if I'm talking nonsense :)

Looking at Chapter 16.2 - Inheritance [1] in Programming in Lua, 
Roberto defines its constructor method like this:

    function Account:new (o)
      o = o or {}
      setmetatable(o, self)
      self.__index = self
      return o
    end

What about redefining it along the following lines for the Lua root 
class, called "LUObject" for the sake of argument:

    function LUObject:new ( anInstance )
      anInstance.super = self
      setmetatable( anInstance, self)
      self.__index = self
      return anInstance
    end

(Not quite sure about the exact syntax and parameters order here, but 
hopefully you get the gist of it :)

When subclassing LUObject, one calls the super class "new" factory 
method, passing itself as an instance:

    function MySubclass:new ()
      return LuaObject( self )
    end

Now there is an explicit class hierarchy between the two objects.

Assuming an existing "description" method in the superclass one would 
like to extend, one could now invoke it like this:

    function MySubclass:description ()
      super:description()

      print "my very own description as well"
    end

Does this make any kind of sense?!?

Thanks!

Cheers

--
PA
http://alt.textdrive.com/


[1] http://www.lua.org/pil/16.2.html