roar-atom

Roar::Atom is a representable back-end that generates Atom feeds. It uses Roar to define the structure of your Atom feed and rAtom to work with the Atom Syndication Format.

Configuration

Add this line to your application's Gemfile:

gem 'roar-atom'

Basics

As Atom feeds follow a very specific structure, we expect representers using the Roar::Atom backend to define a precise set of attributes.

Define a feed

The top-level collection representer defines the <feed> element and should provide the Atom required feed elements:

require 'roar/atom'

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated
end

To render an Atom feed with the representer:

# Given an Avengers class
avengers = Avengers.new(id: 'marvel:avengers',
                        title: 'The Avengers',
                        updated: '2016-12-21T00:00:02Z')

avengers.extend(AvengersAtomFeedRepresenter)
avengers.to_atom
        .to_xml
#=>
# <?xml version="1.0" encoding="UTF-8"?>
# <feed xmlns="http://www.w3.org/2005/Atom">
#   <id>marvel:avengers</id>
#   <title>The Avengers</title>
#   <updated>2016-12-21T00:00:02Z</updated>
# </feed>

Define an entry

An entry should provide the Atom required entry elements.

require 'roar/atom'

class SuperHeroAtomRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated
end

The feed representer accepts a ::collection of entries:

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated

  # Given a SuperHero class
  collection :entries, extend: SuperHeroAtomRepresenter, class: SuperHero
end

Optional constructs

Link and Person elements

Link and Person elements can be used several times in a feed or an entry, so they are represented by a list with the ::collection method.

require 'roar/atom'

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated

  collection :authors
  collection :links
end

These attributes should return an array of hashes:

• with link attributes for a <link> element
• with element names for a <author> or <contributor> element

avengers = Avengers.new(id: 'marvel:avengers',
                        title: 'The Avengers',
                        updated: '2016-12-21T00:00:02Z',
                        authors: [{
                          name: 'Marvel',
                          uri:  'http://marvel.wikia.com',
                          email: 'root@marvel.wikia.com'
                        }],
                        links: [{
                          href:  'http://marvel.wikia.com/wiki/Black_Widow',
                          title: 'Black Widow profile',
                          rel:   'self'
                        }])

avengers.extend(AvengersAtomFeedRepresenter)

avengers.to_atom
        .to_xml

#=>
# <?xml version="1.0" encoding="UTF-8"?>
# <feed xmlns="http://www.w3.org/2005/Atom" xmlns:ns1="http://marvel.wikia.com">
#   ... xml elements
#   <author>
#     <name>Marvel</name>
#     <uri>http://marvel.wikia.com</uri>
#     <email>root@marvel.wikia.com</email>
#   </author>
#   <link href="http://marvel.wikia.com/wiki/Avengers" title="Black Widowprofile" rel="self" />
# </feed>

Optional elements

You can add others feed elements with the ::property method:

# lib/avengers_atom_feed_representer.rb
require 'roar/atom'

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated
  property :rights
end

# avengers_feed.rb
avengers = Avengers.new(id: 'marvel:avengers',
                        title: 'The Avengers',
                        updated: '2016-12-21T00:00:02Z',
                        rights: 'Copyright (c) 1963 Marvel')

avengers.extend(AvengersAtomFeedRepresenter)
avengers.to_atom
        .to_xml

#=>
# <?xml version="1.0" encoding="UTF-8"?>
# <feed xmlns="http://www.w3.org/2005/Atom">
#   ... xml elements
#   <rights>Copyright (c) 1963 Marvel</rights>
# </feed>

Extension elements

As of version 0.3.0, rAtom support simple extension elements on feeds and entries.

To add extension elements, you have to define an xml_namespace to your representer and then, add your element. Example:

# lib/avengers_atom_feed_representer.rb
require 'roar/atom'

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :id
  property :title
  property :updated
  property :custom_friend
end

# avengers_feed.rb
avengers = Avengers.new(id: 'marvel:avengers',
                        title: 'The Avengers',
                        updated: '2016-12-21T00:00:02Z',
                        custom_friend: 'Hawkeye')

avengers.extend(AvengersAtomFeedRepresenter)
avengers.xml_namespace = 'http://marvel.wikia.com'

avengers.to_atom
        .to_xml

#=>
# <?xml version="1.0" encoding="UTF-8"?>
# <feed xmlns="http://www.w3.org/2005/Atom" xmlns:ns1="http://marvel.wikia.com">
#   ... xml elements
#   <ns1:custom_friend>Hawkeye</ns1:custom_friend>
# </feed>

Prefixed representer attributes

Some Atom elements use the same naming as Class attributes (id, title, etc.). In order to avoid recursive attribute changes, you can declare the representer attribute (that stands for an Atom element) with the atom_ prefix. It will return the same feed representer as you would have with regular attributes. Example:

# lib/avengers_atom_feed_representer.rb
require 'roar/atom'

class AvengersAtomFeedRepresenter
  include Roar::Atom::Representer

  property :atom_id
  property :atom_title
  property :atom_updated
  property :atom_custom_friend
end

# avengers_feed.rb
avengers = Avengers.new(id: 'marvel:avengers',
                        title: 'The Avengers',
                        updated: '2016-12-21T00:00:02Z',
                        custom_friend: 'Hawkeye')

avengers.extend(AvengersAtomFeedRepresenter)
avengers.xml_namespace = 'http://marvel.wikia.com'

avengers.to_atom
        .to_xml

#=>
# <?xml version="1.0" encoding="UTF-8"?>
# <feed xmlns="http://www.w3.org/2005/Atom" xmlns:ns1="http://marvel.wikia.com">
#   <id>marvel:avengers</id>
#   <title>The Avengers</title>
#   <updated>2016-12-21T00:00:02Z</updated>
#   <ns1:custom_friend>Hawkeye</ns1:custom_friend>
# </feed>

Development

Setup development:

$ gem install roar
$ gem install ratom
$ gem install rspec 

Test the CLI:

$ rspec .