Ruby: Get all keys in a hash (including sub keys)

Question

let\'s have this hash:

hash = {\"a\" => 1, \"b\" => {\"c\" => 3}}
hash.get_all_keys 
=> [\"a\", \"b\", \"c\"]

how can i get all key

Answer 1

def get_all_keys(hash)
  hash.map do |k, v|
    Hash === v ? [k, get_all_keys(v)] : [k]
  end.flatten
end

Answer 2

hash.keys is the simplest one I have seen to return an array of the key values in a hash.

Answer 3

class Hash

  def get_all_keys
    [].tap do |result|
      result << keys
      values.select { |v| v.respond_to?(:get_all_keys) }.each do |value| 
        result << value.get_all_keys
      end
    end.flatten
  end

end

hash = {"a" => 1, "b" => {"c" => 3}}
puts hash.get_all_keys.inspect # => ["a", "b", "c"]

Answer 4

Here is another approach :

def get_all_keys(h)
  h.each_with_object([]){|(k,v),a| v.is_a?(Hash) ? a.push(k,*get_all_keys(v)) : a << k }
end

hash = {"a" => 1, "b" => {"c" => {"d" => 3}}}
p get_all_keys(hash)
# >> ["a", "b", "c", "d"]