# Assignment as a reference?

**URL:** <https://www.ruby-forum.com/t/assignment-as-a-reference/112530>\
**Category:** Ruby\
**Created:** [August 20, 2007, 6:22pm UTC](https://www.ruby-forum.com/t/assignment-as-a-reference/112530 "2007-08-20T18:22:45Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Morgan\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/57b2e6/32.png) [@Morgan\_G](https://www.ruby-forum.com/u/Morgan_G)\
**Post date:** [August 20, 2007, 6:22pm UTC](https://www.ruby-forum.com/t/assignment-as-a-reference/112530/1 "2007-08-20T18:22:45Z")

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Hi,

I ran into a simple issue earlier with assignment seeming to make  
references. I’m new to Ruby so perhaps this is how it’s supposed to be.  
Here  
is an abridged version of what happened:

foo = ‘bar’ #=\> bar  
foo2 = foo #=\> bar  
foo = foo.gsub ‘bar’, ‘wibble’ #=\> wibble  
foo2 #=\> bar

foo = ‘bar’ #=\> bar  
foo2 = foo #=\> bar  
foo.gsub! ‘bar’, ‘wibble’ #=\> wibble  
foo2 #=\> wibble

You can paste those straight into irb and get the same output. Could  
someone  
please explain why the second example changes foo2?

Cheers,  
Morgan G…

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**Author:** ![Morgan\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/57b2e6/32.png) [@Morgan\_G](https://www.ruby-forum.com/u/Morgan_G)\
**Post date:** [August 20, 2007, 6:26pm UTC](https://www.ruby-forum.com/t/assignment-as-a-reference/112530/2 "2007-08-20T18:26:46Z")

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Hi –

On Tue, 21 Aug 2007, Morgan G. wrote:

> Hi,
> 
> I ran into a simple issue earlier with assignment seeming to make  
> references. I’m new to Ruby so perhaps this is how it’s supposed to be. Here

It is.

> foo2 #=\> wibble
> 
> You can paste those straight into irb and get the same output. Could someone  
> please explain why the second example changes foo2?

Ruby assignments pretty much traffic in references. When you do:

foo2 = foo

you’re giving foo2 a copy of the reference that foo contains. When you  
change the object, you see the change reflected through any reference  
to it.

David

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**Author:** ![Morgan\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/57b2e6/32.png) [@Morgan\_G](https://www.ruby-forum.com/u/Morgan_G)\
**Post date:** [August 20, 2007, 6:29pm UTC](https://www.ruby-forum.com/t/assignment-as-a-reference/112530/3 "2007-08-20T18:29:46Z")

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On 20 Aug 2007, at 17:20, Morgan G. wrote:

> foo = ‘bar’ #=\> bar  
> foo2 = foo #=\> bar  
> foo.gsub! ‘bar’, ‘wibble’ #=\> wibble  
> foo2 #=\> wibble

What you have experienced is reference assignment. If you wish to  
duplicate only the content, and not the reference, then you should to  
use .dup.

> foo = “bar”  
> =\> “bar”  
> foo2 = foo.dup  
> =\> “bar”  
> foo = “wibble”  
> =\> “wibble”  
> foo2  
> =\> “bar”

Hope this helps you out.

Douglas F Shearer  
removed\_email\_address@domain.invalid

> **[Douglas F Shearer](https://douglasfshearer.com/)**
>
> Software developer, mountainbiker.

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<div class="post-metadata">

**Author:** ![Morgan\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/57b2e6/32.png) [@Morgan\_G](https://www.ruby-forum.com/u/Morgan_G)\
**Post date:** [August 20, 2007, 6:35pm UTC](https://www.ruby-forum.com/t/assignment-as-a-reference/112530/4 "2007-08-20T18:35:46Z")

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Thanks for that.

I’ve been reading through quite a few references and manuals (working  
through Agile Web D. at the moment) and the fact that every  
assignment is a reference hasn’t really been mentioned that much. Guess  
I’ve  
missed it or haven’t gotten that far.

Cheers.