Sort hash by values when values are arrays

Question

I have a hash:

hash = {"key1" => [1, a], "key2" => [3, c], "key3" => [2, b]}

I need to sort the hash by the second element of the values like this:

hash = {"key1" => [1, a], "key3" => [2, b], "key2" => [3, c]}

How I can do this?

@Ursus They are ordered as of 1.9. Docs: ruby-doc.org/core-1.9.3/Hash.html "Hashes enumerate their values in the order that the corresponding keys were inserted." — hoffm
– hoffm, Commented Oct 16, 2017 at 20:20

Ursus · Accepted Answer · 2017-10-17 09:29:24Z

2

Try this one

hash.sort_by { |_k, v| v.last }.to_h

edited Oct 17, 2017 at 9:29

answered Oct 16, 2017 at 20:23

Ursus

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hoffm · Accepted Answer · 2017-10-16 20:24:13Z

2

The first thing to note here is that as of Ruby 1.9, Ruby hashes are in fact ordered (docs).

To answer your question, you can use Enumerable#sort_by like so:

hash.sort_by{ |k, v| v[1] }.to_h

This sorts by the second member of each of the value arrays, and returns it as an array of pairs. Then it converts that array of pairs back into a hash (with to_h)

answered Oct 16, 2017 at 20:24

hoffm

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3 Comments

sawa Over a year ago

Ruby 1.9 was released about ten years ago. It's not even maintained anymore. Absolutely no need to mention new features of 1.9. If anyone is sticking to it, its their problem.

hoffm Over a year ago

There was a comment on the question saying that hashes are not ordered. That comment has since been deleted, but that’s what I was reacting to.

Ursus Over a year ago

It was mine, sorry :D

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