Ruby - extracting the unique values per key from an array of hashes

Question

From a hash like the below one, need to extract the unique values per key

array_of_hashes = [ {\'a\' => 1, \'b\' => 2 , \'c\' => 3} , 
                      


        

Answer 1

This is more generic:

options = {}
distinct_keys = array_of_hashes.map(&:keys).flatten.uniq
distinct_keys.each do |k|
  options[k] = array_of_hashes.map {|o| o[k]}.uniq
end

Answer 2

Use Array#uniq:

array_of_hashes = [ {'a' => 1, 'b' => 2 , 'c' => 3} , 
                    {'a' => 4, 'b' => 5 , 'c' => 3}, 
                    {'a' => 6, 'b' => 5 , 'c' => 3} ]

array_of_hashes.map { |h| h['a'] }.uniq    # => [1, 4, 6]
array_of_hashes.map { |h| h['b'] }.uniq    # => [2, 5]
array_of_hashes.map { |h| h['c'] }.uniq    # => [3]