From: Robert Klemme <bob.news@...>
Date: 2004-09-14T19:39:57+09:00
Subject: Re: Singleton method on object via define_method?


"Mauricio Fern�ndez" <batsman.geo@yahoo.com> schrieb im Newsbeitrag
news:20040914095258.GA6742@student.ei.uni-stuttgart.de...
> On Tue, Sep 14, 2004 at 05:34:54PM +0900, Robert Klemme wrote:
> > .... but it might be a good reason to call it "virtual": it simply
doesn't
> > exist the whole time. :-)  OTOH, you can't tell from the outside -
it's
> > there when you need it - lazyly initialized...  ("lazy_class"? Oh
no...)
>
> There's at least one case where you can know if the singleton class has
> been created or not (singletons of singletons).

How come?  What's special about singletons here?

> And you can always know
> if you're using evil.rb, of course :-)

How exactly would you want to do it?  I don't see how eval helps here.

The only way I can imagine is indirect: via instance_methods.  But that
test can only assure, that the singleton class is created, you can't be
sure as long as the difference is empty:

>> s=""
=> ""
>> class << s ; def length() 1 end; end
=> nil
>> s.methods - s.class.instance_methods
=> []
>> class << s ; def foo;"foo"; end; end
=> nil
>> s.methods - s.class.instance_methods
=> ["foo"]

Regards

    robert