Parsed Attributes

This grew out of a need to give structure to the data in HTTP requests and responses. Parsing it was easy enough (Ruby has great gems), but I found myself duplicating a bunch of code to manage the raw and parsed data, exceptions and whatnot.

This was how I fixed that problem.

I'm going to use JSON as the data type for the examples, mostly because it's short to write, and was the first supported data type.

Raw data in, parsed data out.

gem install parsed-attributes

gem gem 'parsed-attributes'

require 'parsed-attributes'

class SomeExampleClass
  extend Parsed::JSON

  json_attribute :data
end

This is a naive hand coded equivalent:

require 'json'

class SomeExampleClass
  attr_reader :raw_data

  def raw_data=(data)
    @raw_data = data
    @parsed_data = nil
    @raw_data
  end

  def parsed_data
    return @parsed_data unless @parsed_data.nil?

    begin
      @parsed_data = JSON.parse @raw_data
    rescue StandardError
      @parsed_data = nil
    end
    @parsed_data
  end
end

The attribute defining methods accept some arguments that modify the way exceptions and un-parseable data are handled.

json_attribute :data

Exceptions during parsing are supressed.

If #raw_data returns un-parseable data, then #parsed_data returns nil.

json_attribute :data, raises_once: true

Exceptions during parsing are propagated the first time after #raw_data= is called, and supressed thereafter.

If #raw_data returns un-parseable data, then #parsed_data returns nil (after the first time).

This setting is mostly for debugging. It allows catching and printing parser exceptions once per data to avoid cluttering up the screen/logs.

This overrides the 'raise always' behavior.

json_attribute :data, raises: true

Exceptions during parsing are always propagated.

Most of the boilerplate code is abstracted away into a helper module, creatively named 'base'.

Extending is really simple, take a look at the JSON parser wrapper for a minimal example.

• JSON
• HTTP Request/Response
  • Generic Headers
  • BasicAuth
  • Cookies
  • Multiple header blocks in Response
• URI