Re: class implementation

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

On Apr 03, 2006, at 21:55, Dolan, Ryanne Thomas (UMR-Student) wrote:

> I think this basic idea could be extended and become quite powerful.  
> Any ideas for improving this system?  Is there another implementation 
> that is inherently faster or more flexible?  Let me know what you 
> think.

Couple of things:

- It would be nice to have the class system tied with Lua's module, so 
one could import a class directly:

local Vector = require( "Vector" )

- Class definition shouldn't pollute the global name space.

- A class should be flexible, supporting 'mixins' (e.g. adding methods 
to the class after the class has been defined). Presently you seem to 
copy the parent(s) methods, preventing any class evolutions.

- Support a bare minimum of reflection (class, className, superclass, 
etc).

- Support parent method invocation when overwriting an implementation 
(e.g. super.init( self ) ).

All in all, I personally much prefer Tomas recent proposal which 
elegantly leverage Lua's built-in module system:

http://lua-users.org/lists/lua-l/2006-03/msg00336.html

Something along these lines:

local function extends( aSuper )
        return function( aClass )
                setmetatable( aClass, aSuper )
                aClass.__index = aClass

                aClass.self = aClass
                aClass.super = aSuper

                return aClass
        end
end

local class = module

class( "Object", extends(), package.seeall )
class( "MyObject", extends( Object ) )

My 2¢.

Cheers

--
PA, Onnay Equitursay
http://alt.textdrive.com/