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 keys since hash.keys returns just ["a", "b"]

Answer 1

This will give you an array of all the keys for any level of nesting.

def get_em(h)   h.each_with_object([]) do |(k,v),keys|           keys << k     keys.concat(get_em(v)) if v.is_a? Hash   end end  hash = {"a" => 1, "b" => {"c" => {"d" => 3}}} get_em(hash) #  => ["a", "b", "c", "d"] 

Answer 2

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.