Best way to convert strings to symbols in hash

For the specific case of YAML in Ruby, if the keys begin with ':', they will be automatically interned as symbols.

require 'yaml'
require 'pp'
yaml_str = "
connections:
  - host: host1.example.com
    port: 10000
  - host: host2.example.com
    port: 20000
"
yaml_sym = "
:connections:
  - :host: host1.example.com
    :port: 10000
  - :host: host2.example.com
    :port: 20000
"
pp yaml_str = YAML.load(yaml_str)
puts yaml_str.keys.first.class
pp yaml_sym = YAML.load(yaml_sym)
puts yaml_sym.keys.first.class

Output:

#  /opt/ruby-1.8.6-p287/bin/ruby ~/test.rb
{"connections"=>
  [{"port"=>10000, "host"=>"host1.example.com"},
   {"port"=>20000, "host"=>"host2.example.com"}]}
String
{:connections=>
  [{:port=>10000, :host=>"host1.example.com"},
   {:port=>20000, :host=>"host2.example.com"}]}
Symbol

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

In Ruby >= 2.5 (docs) you can use:

my_hash.transform_keys(&:to_sym)

Using older Ruby version? Here is a one-liner that will copy the hash into a new one with the keys symbolized:

my_hash = my_hash.inject({}){|memo,(k,v)| memo[k.to_sym] = v; memo}

With Rails you can use:

my_hash.symbolize_keys
my_hash.deep_symbolize_keys 

Here's a better method, if you're using Rails:

params.symbolize_keys

The end.

If you're not, just rip off their code (it's also in the link):

myhash.keys.each do |key|
  myhash[(key.to_sym rescue key) || key] = myhash.delete(key)
end