Convert Ruby array of hashes into one hash

Question

I have the following array:

array = [{"a" => 2}, {"b" => 3}, {"a" => nil}, {"c" => 2}, {"b" => nil}]

I want to convert it into 1 big hash but keep all of the values, so I want it to look like the following:

{"a" => [2, nil], "b" => [3, nil], "c" => [2]}

I can get close doing array.inject({}) {|s, h| s.merge(h)}}, but it overwrites the values.

wouldn't it make more sense to have "c"=> [2] in the hash? — John Dvorak
– John Dvorak, Commented Jul 2, 2013 at 21:01

Arup Rakshit · Accepted Answer · 2013-07-03 19:07:46Z

2

array = [{"a" => 2}, {"b" => 3}, {"a" => nil}, {"c" => 2}, {"b" => nil}]
a = array.each_with_object(Hash.new([])) do |h1,h|
  h1.each{|k,v| h[k] = h[k] + [v]}
end
a # => {"a"=>[2, nil], "b"=>[3, nil], "c"=>[2]}

edited Jul 3, 2013 at 19:07

answered Jul 2, 2013 at 21:13

Arup Rakshit

119k30 gold badges270 silver badges328 bronze badges

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

Comments

Ismael · Accepted Answer · 2013-07-02 21:21:47Z

0

array = [{"a" => 2}, {"b" => 3}, {"a" => nil}, {"c" => 2}, {"b" => nil}]
res = {}

array.each do |hash|
  hash.each do |k, v|
    res[k] ||= []
    res[k] << v
  end
end

answered Jul 2, 2013 at 21:21

Ismael

16.7k6 gold badges63 silver badges76 bronze badges

2 Comments

Mulan Over a year ago

You can get rid of the res[k] ||= [] line if you change res = {} to res = Hash.new []

Ismael Over a year ago

thanks @naomik but I like it this way. There are some strange stuff going on when you use Hash with default values

Collectives™ on Stack Overflow

Convert Ruby array of hashes into one hash

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related