From: "Mikael HÃļilund" <mikael@...>
Date: 2008-04-25T01:07:58+09:00
Subject: Re: Pointer concept in Ruby ?


On Apr 24, 2008, at 18:01, Iņaki Baz Castillo wrote:

> Hi, I'd like to have a variable pointing to a Hash/Array element, so
> if I modify the variable then the Hash/Array element is modified too.
>
> AFAIK this is not possible with Ruby since the abscense of pointer
> concept. I want the following:
>
>  array = [ "aaa", "bbb", "ccc" ]
>
>  a1 = array[1]._some_method_
>  => "bbb"
>
>  a1 = "BBB"
>  => "BBB"
>
>  a[1]
>  => "BBB"
>
> Is it possible in some way? Thanks a lot.
>
>
> --  
> Iņaki Baz Castillo
> <ibc@aliax.net>

Quoth irb:

 >> array = [ "aaa", "bbb", "ccc" ]
=> ["aaa", "bbb", "ccc"]
 >> a1 = array[1]
=> "bbb"
 >> a1.upcase!
=> "BBB"
 >> array
=> ["aaa", "BBB", "ccc"]
 >>

You never pass by value, so you're in essence always dealing with  
pointers.
With your example, you merely made a1 point at a different object, a  
new string, instead of the second string in the array.

If you however call a self-modifying method on a1 while it's pointing  
at the array string, it'll also change in the array, as it's still  
pointing at the same object.

What are you trying to achieve in practice?