Remove nil and blank string in an array in Ruby

Question

I am new to Ruby and stuck with this issue. Let's say I have an array like this:

arr = [1, 2, 's', nil, '', 'd']

and I want to remove nil and blank string from it, i.e. final array should be:

arr = [1, 2, 's', 'd']

I tried compact but it gives this:

arr.compact!
arr #=> [1, 2, 's', '', 'd'] doesn't remove empty string.

I was wondering if there's a smart way of doing this in Ruby.

I checked it, it doesn't have nil, how would you remove nil and empty string at the same time. How's it duplicate? — , Sep 30 '14 at 06:47
blank? returns true for both nil and '' (as well as other things like '/n'). [Docs link](http://api.rubyonrails.org/classes/Object.html#method-i-blank-3F) — Abraham Chan, Sep 30 '14 at 06:48
Yes, `blank?` works but is not available in plain Ruby. It comes with Rails. — awendt, Sep 30 '14 at 06:51
Why downvote? people should atleast give an explanation of a downvote, is this how community help new people here? — , Sep 30 '14 at 06:58
`compact` returns new array, but leave the first array as it is (with `nil` inside). `compact!` changes existing array and returns it (if there will be no `nil` it returns nil). http://www.ruby-doc.org/core-2.0.0/Array.html#method-i-compact — RedZagogulin, Sep 30 '14 at 07:02
@RedZagogulin I read it, the only issue was to remove blank strings and I didn't know about the other operations mentioned in the answers. My question was clear I think, have no idea why people go downvote for no reason without explaining anything. — , Sep 30 '14 at 07:05
@anInteger I don't understand the downvotes either. It's not a duplicate (which IMO is never a reason to downvote anyway), the question is clearly stated and it's clear that you tried to find your own solution. — awendt, Sep 30 '14 at 07:09
@Зелёный blank won't work in Ruby, I hope you know that. :) — , Sep 30 '14 at 07:10
I've fixed this injustice for you. And yes, I agree that it would be nice if people will explain their downvotes. — RedZagogulin, Sep 30 '14 at 07:12
Why was this question marked as a duplicate? It's clearly not a duplicate of the question referenced. — Cary Swoveland, Jun 01 '15 at 16:45

Cary Swoveland · Accepted Answer · 2020-01-14T18:30:49.373

58

You could do this:

arr.reject { |e| e.to_s.empty? } #=> [1, 2, "s", "d"]

Note nil.to_s => ''.

edited Jan 14 '20 at 18:30

answered Sep 30 '14 at 06:49

Cary Swoveland

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For those who see this answer first: as per https://stackoverflow.com/a/41810889/2441263, it's simpler to use `arr.reject(&:blank?)` – lucas Jul 22 '20 at 20:24
Ah! Thanks Cary, my mistake! I was moving too fast and didn't see that comment on the linked answer. Still hope my comment helps rushed folks like me who got here by googling the best way to do this in rails. Maybe not the place for this question, but why the preference for referencing a handle (that can change) over linking directly to the answer? – lucas Jul 24 '20 at 14:28
2

`:blank?`will only work in Rails as it is an ActiveSupport method and not a part of ruby. – pankajdoharey Aug 20 '20 at 09:57

score 27 · Answer 2 · edited May 23 '17 at 11:54

27

Since you want to remove both nil and empty strings, it's not a duplicate of How do I remove blank elements from an array?

You want to use .reject:

arr = [1, 2, 's', nil, '', 'd']
arr.reject { |item| item.nil? || item == '' }

NOTE: reject with and without bang behaves the same way as compact with and without bang: reject! and compact! modify the array itself while reject and compact return a copy of the array and leave the original intact.

If you're using Rails, you can also use blank?. It was specifically designed to work on nil, so the method call becomes:

arr.reject { |item| item.blank? }

edited May 23 '17 at 11:54

Community

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answered Sep 30 '14 at 06:47

awendt

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Integer does not respond to `empty?` – xlembouras Sep 30 '14 at 06:52
Oh. You're absolutely right. Thanks for pointing this out. I updated the answer. – awendt Sep 30 '14 at 06:53
can't upvote because of the low reputation but this is also a nice answer. Also, thank you for the tip but I am not using Rails for now. :) – Sep 30 '14 at 07:12
9

This is the answer I upvote. The way I like to use it is as `arr.reject &:blank?`. – Boris Stitnicky Sep 30 '14 at 10:01
For older versions of ruby you can use `empty?` instead of `blank?` – Wylliam Judd Dec 14 '18 at 19:09
`arr.reject {|e| e.to_s == ''}` is probably easier than `e.nil? || e == ''` – Rob Kinyon Mar 27 '19 at 15:53

score 25 · Answer 3 · answered Jan 23 '17 at 16:20

25

I tend to do:

arr = [1, 2, 's', nil, '', 'd']
arr.reject(&:blank?)

returns:

=> [1, 2, "s", "d"]

answered Jan 23 '17 at 16:20

JayJay

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It wouldn't work as blank? doesn't work on integer or nil class. – Salman Mar 24 '23 at 16:29

score 9 · Answer 4 · answered Aug 31 '20 at 09:36

compact_blank (Rails 6.1+)

If you are using Rails (or a standalone ActiveSupport), starting from version 6.1, there is a compact_blank method which removes blank values from arrays.

It uses Object#blank? under the hood for determining if an item is blank.

[1, 2, 's', nil, '', 'd'].compact_blank
# => [1, 2, 's', 'd']

[1, "", nil, 2, " ", [], {}, false, true].compact_blank
# => [1, 2, true]

Here is a link to the docs and a link to the relative PR.

A destructive variant is also available. See Array#compact_blank!.

Good find! Gives us another good reason to upgrade to Rails 6.1. — Joshua Pinter, Apr 22 '21 at 16:24

Manindra Gautam · Answer 5 · 2017-12-24T07:16:09.387

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arr.reject(&:blank?)

Just use this, no need to anything else.

edited Dec 24 '17 at 07:16

answered Dec 24 '17 at 07:10

Manindra Gautam

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`blank` isn't a Ruby method, it's a Rails one, so you should add the active_support needed library, and the question has tagged Ruby not Rails. Anyways, this answer states something pointed before. – Sebastián Palma Feb 08 '18 at 13:37

potashin · Answer 6 · 2015-07-19T02:50:52.437

4

You can also use - to remove all nil and '' elements:

arr -= [nil, '']
#=> [1, 2, "s", "d"]

Demonstration

Or compact and reject with shortcut (in case you are not using Rails where you can just use arr.reject(&:blank?) ):

arr = arr.compact.reject(&''.method(:==))
#=> [1, 2, "s", "d"]

Demonstration

edited Jul 19 '15 at 02:50

answered Jul 19 '15 at 02:37

potashin

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score 2 · Answer 7 · answered Jun 24 '15 at 06:38

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You can use compact with reject

arr = [1, 2, 's', nil, '', 'd']
arr = [1, 2, 's', 'd']

arr = arr.compact.reject { |h| h == "" }

or

arr = arr.compact.delete_if { |h| h == "" }

answered Jun 24 '15 at 06:38

RockStar

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score 2 · Answer 8 · answered Dec 23 '19 at 08:10

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The simplest and fast way of doing this is :

arr = [1, 2, 's', nil, '', 'd'] - [nil,'']

==> arr = [1, 2, 's', 'd']

answered Dec 23 '19 at 08:10

Jigar Panchal

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score 1 · Answer 9 · answered Sep 30 '14 at 07:23

1

You can use compact and delete_if method to remove nil and blank string in an array in Ruby

arr = [1, 2, 's', nil, '', 'd']
arr.compact!.delete_if{|arrVal| arrVal.class == String and arrVal.empty?}
=> [1, 2, "s", "d"]

answered Sep 30 '14 at 07:23

padmapriya

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Surya · Answer 10 · 2014-09-30T07:30:09.843

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Note: I am considering the array might have string with white spaces in it.

You can do:

arr = [1, 2, 's', nil, ' ', 'd']
arr.reject{|a| a.nil? || (a.to_s.gsub(' ', '') == '') }
#=> [1, 2, "s", "d"]

or:

arr.reject{|a| a.nil? || (a.to_s.gsub(' ', '').empty?) }
#=> [1, 2, "s", "d"]

or if you want to update arr object itself then:

arr.reject!{|a| a.nil? || (a.to_s.gsub(' ', '') == '') } # notice the ! mark, it'll update the object itself.
p arr #=> [1, 2, "s", "d"]

edited Sep 30 '14 at 07:30

answered Sep 30 '14 at 06:50

Surya

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good use case, I'll keep this mind if I come across such situation in future. thanks. – Sep 30 '14 at 07:14

score 0 · Answer 11 · answered Sep 30 '14 at 07:05

0

try this out:

[1, 2, "s", nil, "", "d"].compact.select{|i| !i.to_s.empty?}

answered Sep 30 '14 at 07:05

Sachin Singh

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You might consider using `reject`, rather than `select`, bot to get rid of `!` and because `compact` is also a form of rejection. To me, "reject this and reject that" reads better than "reject this and select that". – Cary Swoveland Sep 30 '14 at 15:43

score 0 · Answer 12 · answered Jul 21 '16 at 09:35

0

Hope this will work for your case :

arr = [1, 2, 's', nil, '', 'd']
arr.select{|x| x.to_s!="" }

answered Jul 21 '16 at 09:35

Varun Gupta

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score 0 · Answer 13 · answered Jul 22 '16 at 02:54

0

I would probably add .strip to eliminate potential whitespace headaches (assuming its not a rails app).

array = [1, 2, "s", nil, "     ", "d", "\n"]
array.reject!{|a| a.nil? || (a.to_s.strip.empty?) }

#=> [1, 2, "s", "d"]

answered Jul 22 '16 at 02:54

Dom

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Remove nil and blank string in an array in Ruby

13 Answers13

compact_blank (Rails 6.1+)