From: Rick DeNatale <rick.denatale@...>
Date: 2008-04-29T20:30:39+09:00
Subject: Re: References in Ruby

On Tue, Apr 29, 2008 at 7:02 AM, Marcin Tyman <m.tyman@interia.pl> wrote:
> Hi guys,
>
>  I was quite a bit confused when write following code:
>
>  a = 10
>  b = a
>  a = 50
>
>  puts b   # -> puts 10
>
>  Why?? Since everything is a reference in Ruby I expected "puts 50".

Well not everything IS a reference in Ruby.  I think you are suffering
from a variation  of the common nuby problem of misunderstanding the
distinction between variables and objects.

Objects have identity and state, sometimes that state is changeable
(only by sending the object a message).

Variables refer to objects.  Variables DON"T refer to other objects.
A variable gets bound to a particular object by assignment, only that
variable's binding gets change by the assignment. Let's step through
your little program

code                      variables                 objects
a = 10                      a ------------------>  10
                                                            ^
b = a                        b----------------------+

This is the situation after the first two lines. But after the third we have:

a = 50                      a -------------------> 50
                                b--------------------> 10

This article might help:
http://talklikeaduck.denhaven2.com/articles/2006/09/13/on-variables-values-and-objects

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/