Building a RSS feed in Ruby on Rails is very easy, it feels like almost built in. We'll use the XML Builder handler that comes with Rails, so let's get started.

Let's assume we want to add the feed to our company blog, made of Article models. Each article has a title and a body property. The ArticlesController is a normal CRUD Rails controller; we'll add the feed to the index action, so let's update that now:

ruby
# app/controllers/articles_controller.rb

class ArticlesController < ApplicationController
  def index
    @articles = Article.last(10)
    respond_to do |format|
      format.html
      format.rss { render :layout => false }
    end
  end
end

The code above just removes the layout from RSS view, which will create next:

html
# app/views/articles/index.rss.builder

xml.instruct! :xml, :version => "1.0"
xml.rss :version => "2.0" do
  xml.channel do
    xml.title "My Company Blog"
    xml.description "This is a blog by My Company"
    xml.link root_url

    @articles.each do |article|
      xml.item do
        xml.title article.title
        xml.description article.body
        xml.pubDate article.published_at.to_s(:rfc822)
        xml.link article_url(article)
        xml.guid article_url(article)
      end
    end
  end
end

Adding the code inside a index.rss.builder file instructs Rails to use Builder Rails handler to handle it and rss as format.

The file creates a RSS 2 file, but we don't use all the fields described in the specification. Notice how the publication date (pubDate) is specified in the required RFC 822 format. Also it's best to show the full URLs to articles, rather than paths.

What's now left to do is add the feed link to the HEAD of our HTML files, so let's add it to the layout file, inside <head> tags:

html
<%= auto_discovery_link_tag :rss, articles_url(:format => :rss) %>

Rails provides auto_discovery_link_tag to create a link tag for the browsers and feed readers. Now if we go to our /articles.rss URL, we should see the feed of our latest 10 blog posts.

Happy coding!