How do I convert a Ruby hash so that all of its keys are symbols?

Question

I have a Ruby hash which looks like:

{ \"id\" => \"123\", \"name\" => \"test\" }

I would like to convert it to:

{ :id         


        

Answer 1

If you are using Rails >= 4 you can use:

hash.deep_symbolize_keys
hash.deep_symbolize_keys!

or

hash.deep_stringify_keys
hash.deep_stringify_keys!

see http://apidock.com/rails/v4.2.1/Hash/deep_symbolize_keys

Answer 2

Victor Moroz provided a lovely answer for the simple recursive case, but it won't process hashes that are nested within nested arrays:

hash = { "a" => [{ "b" => "c" }] }
s2s[hash] #=> {:a=>[{"b"=>"c"}]}

If you need to support hashes within arrays within hashes, you'll want something more like this:

def recursive_symbolize_keys(h)
  case h
  when Hash
    Hash[
      h.map do |k, v|
        [ k.respond_to?(:to_sym) ? k.to_sym : k, recursive_symbolize_keys(v) ]
      end
    ]
  when Enumerable
    h.map { |v| recursive_symbolize_keys(v) }
  else
    h
  end
end

Answer 3

Here's my two cents,

my version of symbolize_keys_deep! uses the original symbolize_keys! provided by rails and just makes a simple recursive call to Symbolize sub hashes.

  def symbolize_keys_deep!(h)
    h.symbolize_keys!
    h.each do |k, v|
      symbolize_keys_deep!(v) if v.is_a? Hash
    end
  end

Answer 4

Here's a Ruby one-liner that is faster than the chosen answer:

hash = {"apple" => "banana", "coconut" => "domino"}
#=> {"apple"=>"banana", "coconut"=>"domino"}

hash.inject({}){|h,(k,v)| h[k.intern] = v; h}
#=> {:apple=>"banana", :coconut=>"domino"}

Benchmark results:

n = 100000

Benchmark.bm do |bm|
  bm.report { n.times { hash.inject({}){|h,(k,v)| h[k.intern] = v; h} } }
  bm.report { n.times { Hash[hash.map{ |k, v| [k.to_sym, v] }] } }
end

# =>       user     system      total        real
# =>   0.100000   0.000000   0.100000 (  0.107940)
# =>   0.120000   0.010000   0.130000 (  0.137966)

Answer 5

Facets' Hash#rekey is also a worth mentioning.

Sample:

require 'facets/hash/rekey'
{ "id" => "123", "name" => "test" }.deep_rekey
=> {:id=>"123", :name=>"test"}

There is also a recursive version:

require 'facets/hash/deep_rekey'
{ "id" => "123", "name" => {"first" => "John", "last" => "Doe" } }.deep_rekey
=> {:id=>"123", :name=>{:first=>"John", :last=>"Doe"}}

Answer 6

Here's a little recursive function to do a deep symbolization of the keys:

def symbolize_keys(hash)
  Hash[hash.map{|k,v| v.is_a?(Hash) ? [k.to_sym, symbolize_keys(v)] : [k.to_sym, v] }]
end