# How can I copy an array and its elements? (call by value) **URL:** \ **Category:** ruby-talk\ **Created:** [7 August 2009 15:18 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793 "2009-08-07T15:18:52Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Janus\_Bor](https://avatars.discourse-cdn.com/v4/letter/j/8e8cbc/32.png) [@Janus\_Bor](https://rubytalk.org/u/Janus_Bor)\ **Post date:** [7 August 2009 15:18 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/1 "2009-08-07T15:18:52Z")
Hi all, I'm failing at something really basic: copying an array and its contents, so that I can modify the copy without modifying the original. Here's an example: irb(main):006:0\> a = [1, 2] =\> [1, 2] irb(main):007:0\> b = a =\> [1, 2] irb(main):008:0\> b.delete(1) =\> 1 irb(main):009:0\> b =\> [2] irb(main):010:0\> a =\> [2] I guess the problem is that arrays are called by name not by value, so that 'b' copy points to the same adress in memory as 'a'. How can I create an independent copy of 'a'? Thanks, Janus > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Fleck\_Jean-Julien](https://avatars.discourse-cdn.com/v4/letter/f/65b543/32.png) [@Fleck\_Jean-Julien](https://rubytalk.org/u/Fleck_Jean-Julien)\ **Post date:** [7 August 2009 15:24 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/2 "2009-08-07T15:24:44Z")
Hello, > I'm failing at something really basic: copying an array and its > contents, so that I can modify the copy without modifying the original. I think the method 'dup' is what you are looking for irb(main):001:0\> a = [1,2] =\> [1, 2] irb(main):002:0\> b = a.dup =\> [1, 2] irb(main):003:0\> b.delete(1) =\> 1 irb(main):004:0\> b =\> [2] irb(main):005:0\> a =\> [1, 2] Cheers, > **···** > > -- > JJ Fleck > PCSI1 Lycée Kleber ---
**Author:** ![as1](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@as1](https://rubytalk.org/u/as1)\ **Post date:** [7 August 2009 15:25 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/3 "2009-08-07T15:25:08Z")
b=a[0..-1] > **···** > > Le Fri, 7 Aug 2009 10:18:52 -0500, Janus Bor \ a écrit : > > > How can I create an independent copy of 'a'? > > -- > Arnaud ---
**Author:** ![sdjkfhwj\_sdlkjfsdkl](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@sdjkfhwj\_sdlkjfsdkl](https://rubytalk.org/u/sdjkfhwj_sdlkjfsdkl)\ **Post date:** [8 August 2009 02:16 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/4 "2009-08-08T02:16:33Z")
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**Author:** ![Janus\_Bor](https://avatars.discourse-cdn.com/v4/letter/j/8e8cbc/32.png) [@Janus\_Bor](https://rubytalk.org/u/Janus_Bor)\ **Post date:** [7 August 2009 15:47 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/5 "2009-08-07T15:47:54Z")
Thank you both, that's exactly what I'm looking for! > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [7 August 2009 16:30 UTC](https://rubytalk.org/t/how-can-i-copy-an-array-and-its-elements-call-by-value/54793/6 "2009-08-07T16:30:09Z")
Just note that #dup and #clone do a shallow copy, so if you modify objects in the copy this change will also be seen via the original Array. Depending on what you do #map might be more appropriate. Kind regards   robert > **···** > > On 07.08.2009 17:47, Janus Bor wrote: > > > Thank you both, that's exactly what I'm looking for! > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/)