How can I group this array of hashes?

Question

I have this array of hashes:

- :name: Ben
  :age: 18
- :name: David
  :age: 19
- :name: Sam
  :age: 18

I need to group them by age

Answer 1

out = {}
array_of_hashes.each do |a_hash|
  out[a_hash[:age]] ||= []
  out[a_hash[:age]] << a_hash
end

or

array.group_by {|item| item[:age]}