Ruby find and return objects in an array based on an attribute

Question

How can you iterate through an array of objects and return the entire object if a certain attribute is correct?

I have the following in my rails app

array_of_objects.each { |favor| favor.completed == false }

array_of_objects.each { |favor| favor.completed }

but for some reason these two return the same result! I have tried to replace each with collect, map, keep_if as well as !favor.completed instead of favor.completed == false and none of them worked!

Any help is highly appreciated!

What I want is to return the entire object `favor` if `favor.completed` and if `!favor.completed` — fardin, Jan 30 '16 at 18:11
Just to qualify @sugar's comment, when it has a block, [Array#each](http://ruby-doc.org/core-2.2.0/Array.html#method-i-each) returns its receiver. — Cary Swoveland, Jan 30 '16 at 19:04
What do you mean by, "return the *entire* object"? Do you mean you want to return an array of those objects from the first array for which a given attribute evaluates `true`? Or evaluates 'false'? — Cary Swoveland, Jan 30 '16 at 19:11
yes that's what I meant. I don't want to have the attribute returned — fardin, Jan 30 '16 at 21:05

score 72 · Accepted Answer · answered Jan 30 '16 at 18:13

72

array_of_objects.select { |favor| favor.completed == false }

Will return all the objects that's completed is false.

You can also use find_all instead of select.

answered Jan 30 '16 at 18:13

Babar Al-Amin

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Are there any non-destructive methods similar to `select`? – Sagar Pandya Jan 30 '16 at 18:30
Didn't understand `non-destructive`, sorry. – Babar Al-Amin Jan 30 '16 at 18:31
`select` changes the original array, I was just wondering if there's a similar specialised method that keeps the original array intact? – Sagar Pandya Jan 30 '16 at 18:35
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No `select` doesn't change `self`. `select!` does. – Babar Al-Amin Jan 30 '16 at 18:45
Oh yes, I see now. Got confused now. – Sagar Pandya Jan 30 '16 at 18:52

Wand Maker · Answer 2 · 2016-01-30T18:23:02.813

15

For first case,

array_of_objects.reject(&:completed)

For second case,

array_of_objects.select(&:completed)

edited Jan 30 '16 at 18:23

answered Jan 30 '16 at 18:11

Wand Maker

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Nicely, done, assuming we both understand the question correctly. btw, I see the wand is no more. – Cary Swoveland Jan 30 '16 at 19:12
@CarySwoveland Thanks for the kind words. – Wand Maker Jan 30 '16 at 19:18
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what does the :& mean? – Jason Cheladyn Apr 18 '18 at 01:21
@liyicky Please refer https://stackoverflow.com/questions/9429819/what-is-the-functionality-of-operator-in-ruby – Wand Maker Apr 18 '18 at 11:52

Arup Rakshit · Answer 3 · 2016-01-30T18:12:21.100

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You need to use Enumerable#find_all to get the all matched objects.

array_of_objects.find_all { |favor| favor.completed == false }

edited Jan 30 '16 at 18:12

answered Jan 30 '16 at 18:10

Arup Rakshit

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both `find` and 'find_all'` are returning nil for me! :( very annoying – fardin Jan 30 '16 at 18:33
this is the array of objects I'm calling them on `[#, #]` – fardin Jan 30 '16 at 18:34

score 0 · Answer 4 · answered Jun 10 '21 at 06:25

0

For newer versions of ruby, you can use filter method

array_of_objects.filter { |favor| favor.completed == false }

Reference: https://apidock.com/ruby/Array/filter

answered Jun 10 '21 at 06:25

prajeesh

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"Newest" means Ruby from 1.8.6_287 ?? (by [your reference](https://apidock.com/ruby/Array/filter)) – Cadoiz Jul 20 '23 at 09:28

Ruby find and return objects in an array based on an attribute

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