Sort an array of array based on the order of another array(Ruby)

Question

I have two arrays like this: arr1 = [name1, name2,name3] and arr2 = [[name1,10], [name3,15], [name2, 20]]. Now I want to sort the arr2 based on the order of arr1. The order of arr2 will change whenever order of arr1 change. I try this:

hash_object = arr2.each_with_object({}) do |obj, hash| 
  hash[obj.name] = obj
end

arr1.map { |index| hash_object[index] }

But the result returned [nil, nil, nil]. I confused of this is the right way, and I only made mistake or are there another ways to solve my problem. Can someone help me?

If future, consider waiting longer before making a selection. There's no rush, and a quick selection can discourage other answers. — Cary Swoveland
– Cary Swoveland, Commented May 26, 2015 at 4:06

spickermann · Accepted Answer · 2015-05-26 04:26:24Z

6

I would do something like this:

arr2.sort_by { |element| arr1.index(element.first) }

edited May 26, 2015 at 4:26

answered May 26, 2015 at 3:24

spickermann

108k9 gold badges115 silver badges147 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Cary Swoveland Over a year ago

Did you mean sort_by? I expected this to raise an exception (since sort takes two arguments), but it returned, [["name2", 20], ["name3", 15], ["name1", 10]], which is not correct, of course.

spickermann Over a year ago

@CarySwoveland: You are right - especially because sort_by is usually faster than sort.

pangpang · Accepted Answer · 2015-05-26 03:28:18Z

1

arr1 = ["name1", "name2", "name3"]
=> ["name1", "name2", "name3"]
arr2 = [["name1",10], ["name3",15], ["name2", 20]]
=> [["name1", 10], ["name3", 15], ["name2", 20]]
arr2.sort_by { |e| arr1.index(e[0]) }
=> [["name1", 10], ["name2", 20], ["name3", 15]]

answered May 26, 2015 at 3:28

pangpang

8,86915 gold badges66 silver badges99 bronze badges

Comments

Cary Swoveland · Accepted Answer · 2015-05-26 03:52:46Z

0

Here's another way:

arr2.values_at(*arr2.map { |str,_| arr1.index(str) })
  #=> [["name1", 10], ["name2", 20], ["name3", 15]]

answered May 26, 2015 at 3:52

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

Collectives™ on Stack Overflow

Sort an array of array based on the order of another array(Ruby)

3 Answers 3

2 Comments

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Linked

Related