# Difference instance variable @ or self

**URL:** <https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740>\
**Category:** Rails\
**Created:** [August 28, 2006, 10:32pm UTC](https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740 "2006-08-28T22:32:31Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![joepmath](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9e8a1a/32.png) [@joepmath](https://www.ruby-forum.com/u/joepmath)\
**Post date:** [August 28, 2006, 10:32pm UTC](https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740/1 "2006-08-28T22:32:31Z")

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First: I’m new to Ruby

Simple model:

class Product \< ActiveRecord::Base

def save  
STDERR \<\< "save: " \<\< @name \<\< “\n”  
STDERR \<\< "save: " \<\< self.name \<\< “\n”  
end  
end

I thought that both lines should give the same result…

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<div class="post-metadata">

**Author:** ![joepmath](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9e8a1a/32.png) [@joepmath](https://www.ruby-forum.com/u/joepmath)\
**Post date:** [August 28, 2006, 10:56pm UTC](https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740/2 "2006-08-28T22:56:32Z")

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I’m pretty new to Ruby myself, I’ve kinda learned as required so I’m  
patchy.

From what I’ve seen however, I think ‘self’ is relative to the current  
scope, i.e instance or class. Where as @ is always in instance scope.

Ian.

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<div class="post-metadata">

**Author:** ![joepmath](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9e8a1a/32.png) [@joepmath](https://www.ruby-forum.com/u/joepmath)\
**Post date:** [August 28, 2006, 11:28pm UTC](https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740/3 "2006-08-28T23:28:43Z")

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self is the object itself.

self.name is saying that there’s a public method on self to be called  
(attr\_reader :name)

@name says ‘get the instance variable @name for this class instance’

Use ‘self’ pretty much the same way you’d use ‘this’ in Java or C++,  
though  
not in the cases that you can use @ (passing yourself to another method  
is  
the most used example).

Jason

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<div class="post-metadata">

**Author:** ![joepmath](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9e8a1a/32.png) [@joepmath](https://www.ruby-forum.com/u/joepmath)\
**Post date:** [August 29, 2006, 12:09am UTC](https://www.ruby-forum.com/t/difference-instance-variable-or-self/66740/4 "2006-08-29T00:09:02Z")

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Hi –

On Mon, 28 Aug 2006, Jason R. wrote:

> > > 
> > 
> > From what I’ve seen however, I think ‘self’ is relative to the current  
> > scope, i.e instance or class. Where as @ is always in instance scope.

self is the “default object”. There’s always one and only one self at  
any point in a Ruby program.

Since classes are objects, self can be a class:

class SelfTest  
p self  
end # =\> output: SelfTest

Instance variables are a way for individual objects (including Class  
objects) to store information and maintain state. Every object has  
its own instance variables.

There’s a tight connection between instance variables and self:  
whenever you see @var, @name, etc., you’re seeing an instance variable  
that belongs to self.

> self is the object itself.
> 
> self.name is saying that there’s a public method on self to be called  
> (attr\_reader :name)

All it really says is that you’re sending the message ‘name’ to the  
object self. Usually you do that in cases where there’s a  
corresponding method – but not always.

attr\_reader isn’t connected to this; there are many methods you can  
call on objects that aren’t created with attr-reader.

> @name says ‘get the instance variable @name for this class instance’

More precisely: @name is the instance variable @name belonging to  
self (whatever self is at that given moment in runtime).

David

–  
David A. Black | removed\_email\_address@domain.invalid  
Author of “Ruby for Rails” [1] | Ruby/Rails training & consultancy [3]  
DABlog (DAB’s Weblog) [2] | Co-director, Ruby Central, Inc. [4]  
[1] [Ruby for Rails](http://www.manning.com/black) | [3] [http://www.rubypowerandlight.com](http://www.rubypowerandlight.com)  
[2] [http://dablog.rubypal.com](http://dablog.rubypal.com) | [4] [http://www.rubycentral.org](http://www.rubycentral.org)