From: Robert Klemme <bob.news@...>
Date: 2003-12-05T20:02:04+09:00
Subject: Re: WeakRef and Object#hash


"Samuel Tesla" <samuel@alieniloquent.com> schrieb im Newsbeitrag
news:87zne8q76l.fsf@hiro.int.procacious.com...
> I'm trying to implement a weak key hash to use for generic objects.
> I'm more than happy to use Object#hash and Object#eql? as they come
> with the distribution, but when I make the WeakRef, the hash values
> don't come out the same way:
>
> irb(main):002:0> a = Object.new
> => #<Object:0x402c9b44>
> irb(main):003:0> a.hash
> => 538332578
> irb(main):004:0> a = WeakRef.new(a)
> => #<Object:0x402c9b44>
> irb(main):005:0> a.hash
> => 538323898
>
> Is this by design, or is this a bug somewhere?

I guess it's by design.  But you can fix this easily by sub classing
WeakRef

class WeakHashRef < WeakRef
  def initialize(*args)
    super
  end

  def hash
    begin
      __getobj__.hash
    rescue WeakRef::RefError
      0
    end
  end

  def eql?(ref)
    begin
      __getobj__.id == ref.__getobj__.id
    rescue WeakRef::RefError
      false
    end
  end
end

Then you need to sub class Hash and override some methods if you want the
WeakHash to look like a normal hash from the outside.

Regards

    robert