param.rb

class Hash
   # Allow accessing to hash elements using full key path separated by comma.
   #
   # hash = {"flash" => {"error" => {"message" => "User type is invalid"}}}
   # hash.param("flash.error.message")
   # # => "User type is invalid"
   #
   def param(key)
      return self[key] unless key.is_a?(String) && key.include?(".")
      key.to_s.split('.').inject(self) do |param, key|
      return unless param
      param[key]
    end
  end
end