From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2008-04-15T10:04:43+09:00
Subject: Re: How to duplicate a object changing the class without attributes memory copy

Iñaki Baz Castillo wrote:
> El Lunes, 14 de Abril de 2008, Gary Wright escribió:
>>  If you just do something like:
>>
>> from_obj.name = header_obj.name
>>
>> You are simply copying object references, you aren't
>> copying all the associated data.
>
> Hi, that's not true: if an attribute is a String then there will be
> memory copy:
>
> class Header
>   attr_accessor :name
> end
>
> class From
>   attr_accessor :name
> end
>
> header = Header.new
> header.name = "AAAA"
> => "AAAA"
>
> from = From.new
> from.name = header.name
> => "AAAA"
>
> from.name = "BBBB"
> => "BBBB"
>
> header.name
> => "AAAA"
>
>
> As you see in the example above if the attribute is a String (or a
> Fixnum and so) attribute copy means memory dupplication.
> Unfortunatelly in my case the attribute is a String.
>
> Regards.

Not true. To verify it, after you do "from.name = header.name", try this:

puts header.name.object_id
puts from.name.object_id

You will see same object id, meaning that you have a reference, not a new object. To make it a copy, do this:

from.name = header.name.dup

Gennady.