recursively_symbolize_keys.rb

class Hash
  def recursively_stringify_keys
    recursively_xify_keys(:to_s, :recursively_stringify_keys)
  end
  
  def recursively_symbolize_keys
    recursively_xify_keys(:to_sym, :recursively_symbolize_keys)
  end
  
  private
    def recursively_xify_keys x, recursion
      inject({}) do |a, (k, v)|
        a[k.respond_to?(x) ? k.send(x) : k] = v.respond_to?(recursion) ?
          v.send(recursion) : v
        a
      end
    end
end