what is the best way to convert a json formatted key value pair to ruby hash with symbol as key?

I am wondering what is the best way to convert a json formatted key value pair to ruby hash with symbol as key: example: { 'user': { 'name': 'foo', 'age': 40, 'location': { 'city' : 'bar', 'state': 'ca' } } } ==> { :user=>{ :name => 'foo', :age =>'40', :location=>{ :city => 'bar', :state=>'ca' } } } Is there a helper method can do this?