From: Lyle Johnson <lyle@...>
Date: 2002-08-07T12:23:12+09:00
Subject: Re: Dup and Clone

"Justin Johnson" <justinj@mobiusent.com> wrote in message
news:3d50209c$1_9@news5.nntpserver.com...
> Could anyone kindly point out the difference between 'dup' and 'clone'?

As has been noted in other responses, they're both kinds of "shallow"
copies. The primary difference is that 'clone' copies an object's *entire*
state, including its freeze status and instance variables, whereas 'dup'
only copies the basic object contents. Why this distinction? That is a dandy
question that I can't answer. Nevertheless, here's a quickie, meaningless
example of the dynamic duo:

    s1 = "This is a string"
    class << s1
      def foo=(f)
        @foo = f
      end
      def foo
        @foo
      end
    end
    s1.foo = 2
    s1.freeze

    s1_clone = s1.clone
    s1_clone.frozen?    --> returns true
    s1_clone.foo    --> returns 2

    s1_dup   = s1.dup
    s1_dup.frozen?    --> returns false
    s1_dup.foo    --> error, basic String class doesn't have a "foo" method

Hope this helps,

Lyle