How can I copy an array and its elements? (call by value)

ruby-talk
1

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/.

2

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

3

b=a[0..-1]

···

Le Fri, 7 Aug 2009 10:18:52 -0500, Janus Bor <janus@urban-youth.com> a écrit :

How can I create an independent copy of 'a'?

--
Arnaud

4

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5

Thank you both, that's exactly what I'm looking for!

···

--
Posted via http://www.ruby-forum.com/.

6

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/