There are a number of ways of parsing an RSS feed in Ruby, but one of the best is a gem called Feedzirra. The main advantage of Feedzirra is its speed; it parses feeds very quickly, but it is also useful as it can parse many different types of feed.

To install Feedzirra we first need to make sure that

is in our list of gem sources. If not we’ll need to add it.

gem sources -a http://gems.github.com

Now we can install the gem:

sudo gem install pauldix-feedzirra

Notice: When I was installing the gem, there are several libs needed, including libcurl4-gnutls-dev libcurl3-gnutls libxslt1-dev, you may not meet this issue, it’s not a big deal, just install what it rely on. Several dependencies will also be installed alongside the gem. Once everything’s installed we’ll need to add a reference to the gem in our application’s /config/environment.rb file.

config.gem "pauldix-feedzirra", :lib => "feedzirra", :source => "http://gems.github.com"

That’s it. We’re ready to start parsing RSS feeds in our application.

Getting start:
Assume that, you’ve got a model to store the feed content which is fetched by the parser, so the model should be like :

class FeedEntry < ActiveRecord::Base
  def self.update_from_feed(feed_url)
    feed = Feedzirra::Feed.fetch_and_parse(feed_url)
    add_entries(feed.entries)
  end

  private
  def self.add_entries(entries)
    entries.each do |entry|
      unless exists? :guid => entry.id
        create!(
          :name         => entry.title,
          :summary      => entry.summary,
          :url          => entry.url,
          :published_at => entry.published,
          :guid         => entry.id
        )
      end
    end
  end
end

A more detailed manual is here!