Referencias a Objetos

Cuando asignamos un valor a una variable no estamos copiando un objeto en esa variable, sólo estamos almacenando una referencia al objeto en esa variable:

>> person1 = "Tim"
=> "Tim"
>> person1.class
=> String
>> person1.object_id
=> 2150445000

>> person2 = person1
=> "Tim"
>> person1[0] = "J"
=> "J"
>> person2
=> "Jim"

El método dup puede ser usado para duplicar un objeto:

>> person2 = person1.dup
=> "Jim"
>> person1[0] = "T"
=> "T"
>> person2
=> "Jim"
>> person1
=> "Tim"

Alternativamente podemos usar el método clone :

>> person2 = person1.clone
=> "Tim"
>> person1[0] = "W"
=> "W"
>> person2
=> "Tim"
>> person1
=> "Wim"

Valores Inmediatos

Los objetos Fixnum son valores inmediatos, no son referencias. Son objetos inmutables.

[16:51][~/Dropbox/Public/LPP/1213(master)]$ irb
ruby-1.9.2-p290 :001 > a = 2
 => 2 
ruby-1.9.2-p290 :002 > b = a
 => 2 
ruby-1.9.2-p290 :003 > b = 5
 => 5 
ruby-1.9.2-p290 :004 > a
 => 2 
ruby-1.9.2-p290 :005 > b
 => 5

Los objetos Symbol son valores inmediatos, no son referencias. Son objetos inmutables.

ruby-1.9.2-p290 :006 > c = :z
 => :z 
ruby-1.9.2-p290 :007 > d = c
 => :z 
ruby-1.9.2-p290 :008 > d = :w
 => :w 
ruby-1.9.2-p290 :009 > c
 => :z 
ruby-1.9.2-p290 :010 > d
 => :w