Deep copy of arrays in Ruby

Question

I wanted to get an object on production and do an exact replica( copy over its contents) to another object of same type. I tried doing this in 3 ways from ruby console which none of them worked:

Let's say you have the tt as the first object you want to copy over and tt2 as the replica object. The first approach I tried is cloning the array
```
tt2.patients  = tt.urls.patients
tt2.doctors   = tt.segments.doctors
tt2.hospitals = tt.pixels.hospitals
```

Second approach I tried is duplicating the array which is actually the same as cloning the array:

tt2.patients  = tt.patients.dup
tt2.doctors   = tt.doctors.dup
tt2.hospitals = tt.hospitals.dup

Third approach I tried is marhsalling.

tt2.patients  = Marshal.load(Marshal.dump(tt.patients)) 
tt2.doctors   = Marshal.load(Marshal.dump(tt.doctors)) 
tt2.hospitals = Marshal.load(Marshal.dump(tt.hospitals))

None of the above works for deep copying from one array to another. After trying out each approach individually above, all the contents of the first object (tt) are nullified (patients, doctors and hospitals are gone). Do you have any other ideas on copying the contents of one object to another? Thanks.

You're merely setting your variables in the first example. Try tt2.patients = tt.patiens.clone instead. — three, Dec 22 '11 at 18:44

score 19 · Answer 1 · edited Jul 07 '16 at 15:27

19

Easy!

@new_tt            = tt2.clone
@new_tt.patients   = tt2.patients.dup
@new_tt.doctors    = tt2.doctors.dup
@new_tt.hospitals  = tt2.hospitals.dup
@new_tt.save

edited Jul 07 '16 at 15:27

BvuRVKyUVlViVIc7

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answered Dec 22 '11 at 18:56

Trip

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This works great. new_tt has all the info I need now. However, all the contents of tt2(patients, doctors,hospitals) are gone after doing what you have told me above. How do you keep the contents of tt2? – Sait Mesutcan Ilhaner Dec 22 '11 at 19:11
Woops! I had a syntactical mistake there. I updated the code above. Try it out. – Trip Dec 23 '11 at 19:14
What is different between this and what his second approach? – Marko Avlijaš Aug 30 '16 at 12:56

score 6 · Answer 2 · edited Jun 20 '20 at 09:12

6

This is what ActiveRecord::Base#clone method is for:

@bar = @foo.clone

@bar.save

edited Jun 20 '20 at 09:12

Community

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answered Dec 22 '11 at 18:54

BvuRVKyUVlViVIc7

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score 2 · Answer 3 · edited Jan 03 '19 at 05:41

2

Ruby Facets is a set of useful extensions to Ruby and has a deep_clone method that might work for you.

edited Jan 03 '19 at 05:41

ggorlen

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answered Dec 22 '11 at 19:20

tadman

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Link doesn't work anymore. New link to [deep_clone is here](https://www.rubydoc.info/github/rubyworks/facets/Kernel:deep_clone). – user1934428 Aug 01 '18 at 08:00

Deep copy of arrays in Ruby

3 Answers3

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