Ruby - explain code snippet hash sorter

Question

I use this code for sorting Hash; I've got no idea how its works. please explain to me:

def foo(hash)
  Hash[hash.sort]
end

irb(main):001:0> h = {1=>'z', 3=>'x', 2=>'y'}
=> {1=>"z", 3=>"x", 2=>"y"}
irb(main):002:0> Hash[h.sort]
=> {1=>"z", 2=>"y", 3=>"x"}
irb(main):003:0>

This can also be written as Hash[hash.sort_by(&:first)], where hash.sort_by(&:first) sorts the key-value pairs by key. If the hash is large this may be faster than using sort. — Cary Swoveland
– Cary Swoveland, Commented Nov 22, 2019 at 6:55

falsetru · Accepted Answer · 2014-10-23 15:02:36Z

1

Enumerable#sort reutrns an sorted array of key-value pairs:

h = {b: 1, a: 2}
h.sort
# => [[:a, 2], [:b, 1]]

Hash::[] create a new hash base on the argument:

Hash[h.sort]
# => {:a=>2, :b=>1}

BTW, if you use Ruby 2.1+, you can use Array#to_h instead:

h.sort.to_h
# => {:a=>2, :b=>1}

edited Oct 23, 2014 at 15:02

answered Oct 23, 2014 at 14:56

falsetru

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3 Comments

BroiSatse Over a year ago

For completeness: in ruby v2 you can just do h.sort.to_h

jc newb Over a year ago

i swear firts things i did was to look in the doc;

falsetru Over a year ago

@BroiSatse, Thank you for comment. I updated the answer to include Array#to_h. BTW, it's introduced in Ruby 2.1.

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