From: James Gray <james@...>
Date: 2008-12-29T02:25:35+09:00
Subject: Re: New to Ruby: copying arrays?

On Dec 28, 2008, at 5:02 AM, Stefano Crocco wrote:

> Alle Sunday 28 December 2008, John Park ha scritto:
>> Oh, one more question: what's the difference between .dup and .clone
>> methods?
>
> As far as I know, the only difference is that clone also copies the  
> frozen
> state of the original object, while dup doesn't:
> s1 = "test"
> s1.freeze
> s2 = s1.dup
> s3 = s1.clone
> puts s2.frozen? #=> false
> puts s3.frozen? #=> true

clone() also copies an object's singleton class:

   >> s = "cat"
   => "cat"
   >> def s.speak; "purr" end
   => nil
   >> s.speak
   => "purr"
   >> s.dup.speak
   NoMethodError: undefined method `speak' for "cat":String
   	from (irb):4
   >> s.clone.speak
   => "purr"

I learned this and other great things from these screencasts:

   http://www.pragprog.com/screencasts/v-dtrubyom/the-ruby-object-model-and-metaprogramming

James Edward Gray II