RSS and ATOM feeds

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Sunday, 14 September 2008

One thing that I really had to include in Matilda was the ability to generate RSS or ATOM feeds, it being a blogging engine it's sort of expected ;-)

So after hunting around I eventually managed to build a set of actions for my blog controller to generate the xml data.

Actions

Below are the two actions which will sift thru the database and return an object containing all relevant records, one for atom, one for rss (yep i could combine them but this is early days). Put something similar in your blog_controller.rb

def feed_atom
  @articles = Article.find(:all,
      :limit => Settings.rss_count,
      :order => 'created_at DESC',
      :conditions => ['article_type_id = 1 and publish = 1'])
  respond_to do |format|
    format.atom
  end
end

def feed_rss
  @articles = Article.find(:all,
      :limit => Settings.rss_count,
      :order => 'created_at DESC',
      :conditions => ['article_type_id = 1 and publish = 1'])
  respond_to do |format|
    format.rss
  end
end

Builders

Now in your view create two builders, one to generate each type of xml data,

(in feed_atom.atom.builder)

xml.instruct! :xml, :version=>"1.0" 
xml.feed(:xmlns => "http://www.w3.org/2005/Atom") do |feed|
  feed.title(Settings.blog_title.camelize + ' ' + Settings.blog_subtitle)
  feed.link('http://www.myblog.com')
  for article in @articles do
    feed.entry do |entry|
      entry.title(article.title)
      entry.content(article.filter_body, :type => 'text')
      entry.updated(article.created_at)
      entry.link("http://www.myblog.com/"+article.url)
    end
  end
end

(in feed_rss.rss.builder)

xml.instruct! :xml, :version => "1.0"
xml.rss :version => "2.0" do
  xml.channel do
    xml.title Settings.blog_title.camelize
    xml.description Settings.blog_subtitle
    xml.link "http://www.myblog.com"

    for article in @articles
      xml.item do
        xml.title article.title
        xml.description article.filter_body
        xml.pubDate article.created_at.to_s(:rfc822)
        xml.link "http://www.myblog.com/"+article.url
      end
    end
  end
end

It's pretty straightforward, the article.url is a method i've got in my model that generates the right url for the article, filter_body converts the body text into html based on whether that article was stored using textile, markdown or plain text.

Routes

Now add these into your routes.rb so you can linkup the actions how you want them,

map.connect 'feed.atom', :controller => 'blog', :action => 'feed_atom'
map.connect 'feed.rss', :controller => 'blog', :action => 'feed_rss'

...once done, anyone hitting www.myblog.com/feed.rss will get the rss feed, or /feed.atom for their atom feed; whichever floats their boat.

AutoDiscovery

Finally, the most important bit, adding autodiscovery links to the head of your web-page so your visitors browsers can automatically see and consume your feeds.

<head>
<link href='http://www.myblog.com/feed.atom' rel='alternate' title='ATOM' type='application/atom+xml' />
<link href='http://www.myblog.com/feed.rss' rel='alternate' title='RSS' type='application/rss+xml' />
</head>

Now whenever anyone hits your blog their browser will show the common ))) arrows at the right-corner of the address bar saying there's a feed to consume, when they click it they can choose which type of feed they want to subscribe to.

I'm probably missing out on a few things but it's enough to get you started, enjoy!

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