Best way to convert strings to symbols in hash

Question

What\'s the (fastest/cleanest/straightforward) way to convert all keys in a hash from strings to symbols in Ruby?

This would be handy when parsing YAML.

Answer 1

In Rails you can use:

{'g'=> 'a', 2 => {'v' => 'b', 'x' => { 'z' => 'c'}}}.deep_symbolize_keys!

Converts to:

{:g=>"a", 2=>{:v=>"b", :x=>{:z=>"c"}}}

Answer 2

if you're using Rails, it is much simpler - you can use a HashWithIndifferentAccess and access the keys both as String and as Symbols:

my_hash.with_indifferent_access 

see also:

http://api.rubyonrails.org/classes/ActiveSupport/HashWithIndifferentAccess.html

---

Or you can use the awesome "Facets of Ruby" Gem, which contains a lot of extensions to Ruby Core and Standard Library classes.

  require 'facets'
  > {'some' => 'thing', 'foo' => 'bar'}.symbolize_keys
    =>  {:some=>"thing", :foo=>"bar}

see also: http://rubyworks.github.io/rubyfaux/?doc=http://rubyworks.github.io/facets/docs/facets-2.9.3/core.json#api-class-Hash

Answer 3

How about this:

my_hash = HashWithIndifferentAccess.new(YAML.load_file('yml'))

# my_hash['key'] => "val"
# my_hash[:key]  => "val"

Answer 4

ruby-1.9.2-p180 :001 > h = {'aaa' => 1, 'bbb' => 2}
 => {"aaa"=>1, "bbb"=>2} 
ruby-1.9.2-p180 :002 > Hash[h.map{|a| [a.first.to_sym, a.last]}]
 => {:aaa=>1, :bbb=>2}

Answer 5

If you are using json, and want to use it as a hash, in core Ruby you can do it:

json_obj = JSON.parse(json_str, symbolize_names: true)

symbolize_names: If set to true, returns symbols for the names (keys) in a JSON object. Otherwise strings are returned. Strings are the default.

Doc: Json#parse symbolize_names

Answer 6

This is my one liner for nested hashes

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