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

**URL:** <https://www.ruby-forum.com/t/re-final-closed-classes-in-ruby-was-sharp-knives-and-glue/94737>\
**Category:** Ruby\
**Created:** [May 12, 2006, 4:07pm UTC](https://www.ruby-forum.com/t/re-final-closed-classes-in-ruby-was-sharp-knives-and-glue/94737 "2006-05-12T16:07:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![BergerS\_Daniel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bc8723/32.png) [@BergerS\_Daniel](https://www.ruby-forum.com/u/BergerS_Daniel)\
**Post date:** [May 12, 2006, 4:07pm UTC](https://www.ruby-forum.com/t/re-final-closed-classes-in-ruby-was-sharp-knives-and-glue/94737/1 "2006-05-12T16:07:27Z")

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> -----Original Message-----  
> From: Logan C. [[mailto:removed\_email\_address@domain.invalid](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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**Author:** ![BergerS\_Daniel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bc8723/32.png) [@BergerS\_Daniel](https://www.ruby-forum.com/u/BergerS_Daniel)\
**Post date:** [May 12, 2006, 9:45pm UTC](https://www.ruby-forum.com/t/re-final-closed-classes-in-ruby-was-sharp-knives-and-glue/94737/2 "2006-05-12T21:45:00Z")

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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.