From: "David A. Black" <dblack@...>
Date: 2008-10-31T02:55:39+09:00
Subject: Re: Problem with copying array

Hi --

On Fri, 31 Oct 2008, Alan Slater wrote:

> Highly related newbie question, please pardon the non-technical
> language.
>
> So, arrays (even arrays of 'primitives' like strings) don't actually
> contain the objects that fill each entry, they instead (effectively)
> link to those objects. So, .delete_at and .slice! (for example) don't
> remove things from the array, they delete the objects that are being
> linked to completely.
>
> This explains my problem (why, whenever I delete an entry from an array,
> it also deletes it from every copy of the array).
>
> So, how could I simply remove an object from an array, without deleting
> the object itself? Something like, array_name.remove_at(x) (except
> obviously that doesn't exist).
>
> I've been through the API and can't find anything that seems to fit. I
> tried array_name[x] = nil, but that just left an empty entry and didn't
> change the length of the array. Even that seems to change the original
> object to nil too, as following array_name[x] = nil with
> array.delete_at(x) removes the equivalent entry  from the original array
> as well.
>
> How can I remove an entry from an array without deleting the object that
> the entry refers to?

Removing an entry from an array never destroys the object.


   s = "string"
   a = [s]
   a.clear
   p a         # []
   p s         # "string"

As long as a reference to the object exists, the object will still be
available. Objects don't even know whether or not they are in
collections.


David

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