From: dblack@...
Date: 2006-12-08T07:45:22+09:00
Subject: Re: Array changing after concat function

Hi --

On Fri, 8 Dec 2006, Drew Olson wrote:

> WKC CCC wrote:
>> I've found that using:
>>
>> copy = one.map { |el| el.clone }
>>
>> will copy all elements into the new array without referring to the same
>> object.
>> Is there a reason why the clone function has been ommitted from the API
>> doc?
>
> It seems much simpler to just clone the array rather than each element
> individually:
>
> irb(main):001:0> a=[]
> => []
> irb(main):002:0> 10.times{|i| a << i}
> => 10
> irb(main):003:0> a
> => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> irb(main):004:0> b = a.clone
> => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> irb(main):005:0> a[0] = 10
> => 10
> irb(main):006:0> a
> => [10, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> irb(main):007:0> b
> => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

But that won't do a deep cloning, which is what it sounds like WKC
wants:

irb(main):001:0> a = [""]
=> [""]
irb(main):002:0> a[0].object_id
=> -604580558
irb(main):003:0> a.clone[0].object_id
=> -604580558
irb(main):004:0> a.map {|e| e.clone }[0].object_id
=> -604623258


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org