How to delete a element from two arrays independently which has been copied from one another?

Question

a = [1,2,3]

=> [1, 2, 3]

b = a

=> [1, 2, 3]

b.delete(1)

=> 1

b

=> [2, 3]

a

=> [2, 3]

Array A has given [1,2,3] values, and Array A has been copied to Array B

Then whenever I delete a element from Array B , the element gets deleted from Array A too

eg : If i delete element 1 from array B ,it gets deleted from array A too..

How to avoid this, How to delete an element from these arrays separately ?

"Array A has been copied to Array B" – Where? There is no copy operation in your code. — Jörg W Mittag, Jan 05 '17 at 00:06

Coolness · Accepted Answer · 2017-01-04T20:13:11.360

3

You can use dup to create a copy of the array.

a = [1,2,3]
=> [1, 2, 3]
b = a.dup
=> [1, 2, 3]
a.delete(1)
=> 1
a
=> [2, 3]
b
=> [1, 2, 3]

EDIT:

As to why this is, when you assign b = a, you assign b to be a reference to a. This means that both variables refer the same underlying object. With dup we are forcing Ruby to create a copy of a.

edited Jan 04 '17 at 20:13

answered Jan 04 '17 at 19:47

Coolness

1,932
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Thanks a lot, It worked and can I know why it was happening? – alert pay Jan 04 '17 at 19:50
On the subtleties of clone vs dup: http://stackoverflow.com/questions/10183370/whats-the-difference-between-rubys-dup-and-clone-methods – tokland Jan 04 '17 at 19:51
Updated the answer :) – Coolness Jan 04 '17 at 19:53
@CarySwoveland Thanks for the note, I'll remove them. – Coolness Jan 04 '17 at 20:11

score 0 · Answer 2 · answered Jan 04 '17 at 19:49

0

You are creating a shallow copy in b, so the contents aren't copied. To copy them, use Object::clone: b = a.clone.

answered Jan 04 '17 at 19:49

Innot Kauker

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How to delete a element from two arrays independently which has been copied from one another?

2 Answers2