From: Nathan <nathan@...>
Date: 2009-10-14T06:15:10+09:00
Subject: Re: Class Level inheritable attributes - are we there yet?

On 2009-10-13 14:57:25 -0400, Robert Klemme <shortcutter@googlemail.com> said:

> On 13.10.2009 20:07, Dreamcat Four wrote:
>> Robert Klemme wrote:
>>> My understanding of the above is this.  You have two use cases in mind:
>>> 
>>> 1. Inheriting dynamic attribute values defining a proximity rule, i.e.
>>> when asked you get the closest attribute.
>> 
>> Yes. I have been using this way for the YamlDoc Gem
>> 
>>> 2. Constants which with the same proximity lookup rule as above only
>>> that values do not change after the initialization.
>> 
>> No. I dont suggest that.
> 
> Well, it _is_ in the language already.

I prefer the constant way:

class A
  Foo = 2
  def self.foo
    self::Foo
  end
end
class B < A; end
class C < A
  Foo = 4
end
class D < C; end
class E < D
  Foo = 6
end
[A, B, C, D, E].map { |k| k.foo } # => [2, 2, 4, 4, 6]


I would vote that @@ be changed to be treated in the same way constants 
are now (or even to be a getter/setter for a constant of the same 
name), stored in original and looked up in the chain, that way they can 
be overriden locally but don't need to be _forcefully copied_ down into 
each and every class.

Deep (or any other) copy doesn't seem like a good idea at all to me.

--
Nathan