From: Gavin Kistner <gavin.kistner@...>
Date: 2006-09-13T01:17:24+09:00
Subject: Duplication from a Subclass, Object#become

I know that this has been discussed before, but searching has not turned
up the definitive answers I had hoped for.

I'm stuck in a situation like this:

  class Foo
    def dup
      # strange, magical, important things happen here
      # which know about all of Foo's instance variables
    end
  end

  class Bar < Foo
    def dup
      super
    end
  end

  b1 = Bar.new
  b2 = b2.dup
  p b2.class   #=> Foo

How do I get around it? Is subclassing inherently a problem here, and I
need to wrap-and-delegate to a foo instance held by my bar instance?

Will evil.rb ever be part of a standard Ruby distribution, so I could
do:
  class Bar < Foo
    def dup
      klone = super
      klone.class = Bar
      klone
    end
  end