From: dblack@...
Date: 2006-01-27T02:35:52+09:00
Subject: Re: Class is object? :very_sleepy

Hi --

On Fri, 27 Jan 2006, Lionel Thiry wrote:

>> What I would really like is a better metaphore for class!
>> Thanks!
>
> Objects generally don't like to hold their methods themselves, that's
> why they ask for other objects, called classes, to hold them. Those
> objects are smart and they gather the burden of methods with other
> objects, some of them are called modules, while the others are classes.
>
> Sometimes, an object like to hold a method without help. It wants to do
> it itself, alone, as if it was a singleton, the unique object of its
> kind in the universe. That's why those kind of methods are called
> "singleton methods".
>
> In ruby, even singleton methods are not truly hold by the object itself,
> even if all goes as if it was. A singleton method is hold by a special
> object whose name is still hard to define (singleton class, eigenclass,
> metaclass, etc...).

(Singleton class was the last term I heard Matz say he was using :-)

The point about objects not holding methods is so important.  People
sometimes talk about "adding methods to objects", and then get tripped
up about method lookup order.  It's more a matter of the object
meandering through classes and modules, in a certain order, trying to
find a match for a message it's received.


David

-- 
David A. Black
dblack@wobblini.net

"Ruby for Rails", from Manning Publications, coming May 1, 2006!
http://www.manning.com/books/black