ActionView::Helpers::AtomFeedHelper

Adds easy defaults to writing Atom feeds with the Builder template engine (this does not work on ERb or any other template languages).

Full usage example:

  config/routes.rb:
    Basecamp::Application.routes.draw do
      resources :posts
      root :to => "posts#index"
    end

  app/controllers/posts_controller.rb:
    class PostsController < ApplicationController::Base
      # GET /posts.html
      # GET /posts.atom
      def index
        @posts = Post.find(:all)

        respond_to do |format|
          format.html
          format.atom
        end
      end
    end

  app/views/posts/index.atom.builder:
    atom_feed do |feed|
      feed.title("My great blog!")
      feed.updated(@posts.first.created_at)

      for post in @posts
        feed.entry(post) do |entry|
          entry.title(post.title)
          entry.content(post.body, :type => 'html')

          entry.author do |author|
            author.name("DHH")
          end
        end
      end
    end

The options for atom_feed are:

• :language: Defaults to “en-US”.

• :root_url: The HTML alternative that this feed is doubling for. Defaults to / on the current host.

• :url: The URL for this feed. Defaults to the current URL.

• :id: The id for this feed. Defaults to “tag:#{request.host},#{options[:schema_date]}:#{request.request_uri.split(".")}“

• :schema_date: The date at which the tag scheme for the feed was first used. A good default is the year you created the feed. See feedvalidator.org/docs/error/InvalidTAG.html for more information. If not specified, 2005 is used (as an “I don’t care” value).

• :instruct: Hash of XML processing instructions in the form {target => {attribute => value, }} or {target => [{attribute => value, }, ]}

Other namespaces can be added to the root element:

  app/views/posts/index.atom.builder:
    atom_feed({'xmlns:app' => 'http://www.w3.org/2007/app',
        'xmlns:openSearch' => 'http://a9.com/-/spec/opensearch/1.1/'}) do |feed|
      feed.title("My great blog!")
      feed.updated((@posts.first.created_at))
      feed.tag!(openSearch:totalResults, 10)

      for post in @posts
        feed.entry(post) do |entry|
          entry.title(post.title)
          entry.content(post.body, :type => 'html')
          entry.tag!('app:edited', Time.now)

          entry.author do |author|
            author.name("DHH")
          end
        end
      end
    end

The Atom spec defines five elements (content rights title subtitle summary) which may directly contain xhtml content if :type => ‘xhtml’ is specified as an attribute. If so, this helper will take care of the enclosing div and xhtml namespace declaration. Example usage:

   entry.summary :type => 'xhtml' do |xhtml|
     xhtml.p pluralize(order.line_items.count, "line item")
     xhtml.p "Shipped to #{order.address}"
     xhtml.p "Paid by #{order.pay_type}"
   end

atom_feed yields an AtomFeedBuilder instance. Nested elements yield an AtomBuilder instance.

     # File lib/action_view/helpers/atom_feed_helper.rb, line 96
 96:       def atom_feed(options = {}, &block)
 97:         if options[:schema_date]
 98:           options[:schema_date] = options[:schema_date].strftime("%Y-%m-%d") if options[:schema_date].respond_to?(:strftime)
 99:         else
100:           options[:schema_date] = "2005" # The Atom spec copyright date
101:         end
102: 
103:         xml = options.delete(:xml) || eval("xml", block.binding)
104:         xml.instruct!
105:         if options[:instruct]
106:           options[:instruct].each do |target,attrs|
107:             if attrs.respond_to?(:keys)
108:               xml.instruct!(target, attrs)
109:             elsif attrs.respond_to?(:each)
110:               attrs.each { |attr_group| xml.instruct!(target, attr_group) }
111:             end
112:           end
113:         end
114: 
115:         feed_opts = {"xml:lang" => options[:language] || "en-US", "xmlns" => 'http://www.w3.org/2005/Atom'}
116:         feed_opts.merge!(options).reject!{|k,v| !k.to_s.match(/^xml/)}
117: 
118:         xml.feed(feed_opts) do
119:           xml.id(options[:id] || "tag:#{request.host},#{options[:schema_date]}:#{request.fullpath.split(".")[0]}")
120:           xml.link(:rel => 'alternate', :type => 'text/html', :href => options[:root_url] || (request.protocol + request.host_with_port))
121:           xml.link(:rel => 'self', :type => 'application/atom+xml', :href => options[:url] || request.url)
122: 
123:           yield AtomFeedBuilder.new(xml, self, options)
124:         end
125:       end