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

I find grep useful here:

def get_keys(hash)
  ( hash.keys + hash.values.grep(Hash){|sub_hash| get_keys(sub_hash) } ).flatten
end

p get_keys my_nested_hash #=> ["a", "b", "c"]

I like the solution as it is short, yet it reads very nicely.