From: Simon Strandgaard <neoneye@...>
Date: 2004-03-08T19:19:41+09:00
Subject: Re: proposal:  class<<obj to invoke extend_object

On Mon, 08 Mar 2004 12:58:45 +0900, Yukihiro Matsumoto wrote:
>     on 04/03/08, Simon Strandgaard <neoneye@adslhome.dk> writes:
> |> Describe yourself deeper.  What exactly is your proposal? 
> |
> |When 'class<<obj' is seen by Ruby, then an init method should be invoked.
> |I propose to reuse #extend_object and #extended for this.
> |
> |> And why do you think it's needed?
> |
> |Its difficult to add an new instance variable to obj.
> |Its inflexible compared to obj.extend(Mod), because there isn't
> |invoked an #extend_object method when the extension occurs.
> 
> You didn't explain why you need "extended" for singleton class
> definition.  Why don't you use extend for your purpose, before
> changing the language?

I don't have a serious need for 'class<<obj'.

I have recently initiated working on a book about testing, with a few 
chapters about Ruby. My first attempt of making an good example of how
to use the 'class<<obj', I discovered that no init method got invoked.
Thus I got curious to if that was a missing feature.

My initial thought were first to describe 'obj.extend(Mod)' and next
describe 'class<<obj' as being similar, but this isn't true.
So its probably better to describe them in separate. 

 
> |> Remember, since singleton class always exists for each object
> |> (virtually), 'class <<obj' is rather corresponds to class re-opening.
> |
> |I am only little familiar with class re-opening..
> 
> I want you to take a break and learn about Ruby before claiming apples
> and oranges are similar.  Yes, they are.  But not the same.  Besides
> that, singleton class definition is a kind of class re-opening, so
> that they should remain same.

Ok, I am learning every day ;-)


> Class re-opening is a class definition whose target is an existing
> class, for example:
> 
>   class String
>     def foo     # String#foo become available
>     end
>   end
> 
> there's no hook for class re-opening.
> 

I wasn't sure about what kind of reopening you talked about in last mail.
Yes, I have used this a few times. However I am only interested in
modifying a specific instance with 'class<<obj'.


Sorry for todays noise.  ;-)

--
Simon Strandgaard