# Assignment as a reference? **URL:** \ **Category:** ruby-talk\ **Created:** [20 August 2007 16:20 UTC](https://rubytalk.org/t/assignment-as-a-reference/40060 "2007-08-20T16:20:42Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Morgan\_Grubb](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@Morgan\_Grubb](https://rubytalk.org/u/Morgan_Grubb)\ **Post date:** [20 August 2007 16:20 UTC](https://rubytalk.org/t/assignment-as-a-reference/40060/1 "2007-08-20T16:20:42Z")
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 Grubb. ---
**Author:** ![David\_A\_Black1](https://avatars.discourse-cdn.com/v4/letter/d/bcef8e/32.png) [@David\_A\_Black1](https://rubytalk.org/u/David_A_Black1)\ **Post date:** [20 August 2007 16:24 UTC](https://rubytalk.org/t/assignment-as-a-reference/40060/2 "2007-08-20T16:24:14Z")
Hi -- > 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. > 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? 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 > **···** > > On Tue, 21 Aug 2007, Morgan Grubb wrote: > > -- > \* Books: >    RAILS ROUTING (new! [http://www.awprofessional.com/title/0321509242\](http://www.awprofessional.com/title/0321509242%5C)) >    RUBY FOR RAILS ([http://www.manning.com/black\](http://www.manning.com/black%5C)) > \* Ruby/Rails training >      & consulting: Ruby Power and Light, LLC ([http://www.rubypal.com](http://www.rubypal.com)) ---
**Author:** ![Douglas\_F\_Shearer](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Douglas\_F\_Shearer](https://rubytalk.org/u/Douglas_F_Shearer)\ **Post date:** [20 August 2007 16:28 UTC](https://rubytalk.org/t/assignment-as-a-reference/40060/3 "2007-08-20T16:28:22Z")
> 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 dougal.s@gmail.com > **[Douglas F Shearer](https://douglasfshearer.com/)** > > Software developer, mountainbiker. > **···** > > On 20 Aug 2007, at 17:20, Morgan Grubb wrote: ---
**Author:** ![Morgan\_Grubb](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@Morgan\_Grubb](https://rubytalk.org/u/Morgan_Grubb)\ **Post date:** [20 August 2007 16:34 UTC](https://rubytalk.org/t/assignment-as-a-reference/40060/4 "2007-08-20T16:34:05Z")
Thanks for that. I've been reading through quite a few references and manuals (working through Agile Web Development 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. > **···** > > On 20/08/07, Douglas F Shearer \ wrote: > > > On 20 Aug 2007, at 17:20, Morgan Grubb 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 > > dougal.s@gmail.com > > [http://douglasfshearer.com](http://douglasfshearer.com)