Re: final/closed classes in Ruby (was: Sharp knives and glue


#1

-----Original Message-----
From: Logan C. [mailto:removed_email_address@domain.invalid]
Sent: Thursday, May 11, 2006 5:18 PM
To: ruby-talk ML
Subject: Re: final/closed classes in Ruby (was: Sharp knives and glue)

Unfortunately, it raises an exception way too late.

Too late for whom? Yes, you can get around it, but you have to go out
of your way to do so.

Dan

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#2

On May 12, 2006, at 10:05 AM, Berger, Daniel wrote:

of your way to do so.
in error, please immediately notify the sender by reply e-mail and
destroy
all copies of the communication and any attachments.

I’m defining too late as ‘after the damage has been done’, e.g. Bar
has already been sub-classed. I guess it comes down to a question of
does final mean no sub-classes can be created, or no sub-classes can
be used? If it means the first, than yes it is too late. I think that
the distinction is especially important in Ruby because we do have
these #inherited style hooks, and inheriting from something can
cause all sorts of side effects (e.g. activerecord). If someone does
something like

class A < SomeClassFullOfDeepMagic
final # don’t want any subclasses of A
end

class B < A
end

and expects it to work, they may be in for a rude surprise, since the
deep magic may still happen, despite the fact that an exception is
raised.