atom_feed,rss

http://railscasts.com/episodes/87-generating-rss-feeds
http://svn.rubyonrails.org/rails/plugins/atom_feed_helper/README
http://api.rubyonrails.com/classes/ActionView/Helpers/AtomFeedHelper.html#M001208
http://hideto.javaeye.com/blog/84463
http://snippets.dzone.com/tags/ruby/blinksale
http://railspikes.com/2008/10/1/publishing-non-activerecord-objects-in-an-atom-feed-with-rails

atom_feed do |feed|
 feed.title("All User Books!")
 feed.updated((@users.first.created_at))

 for user in @users
   feed.entry(user) do |entry|
     entry.title(user.name)
     entry.content(user.name, :type => 'html')

     entry.books do |books|  <= 幹 這個地方不用再傳東西, entry.book(fuck)
       for b in user.books
         books.title(b.name)
       end
     end
   end
 end
end

<?xml version="1.0" encoding="UTF-8"?> 
<feed xml:lang="en-US" xmlns="http://www.w3.org/2005/Atom">
 <id>tag:localhost,2005:/people</id>
 <link type="text/html" rel="alternate" href="http://localhost:25001"/>
 <link type="application/atom+xml" rel="self" href="http://localhost:25001/people.atom"/>
 <title>My great blog!</title>
 <updated>2008-11-04T00:31:17Z</updated>
 <entry>
   <id>tag:localhost,2005:User/1</id>
   <published>2008-11-04T00:31:17Z</published>
   <updated>2008-11-04T00:31:17Z</updated>
   <link type="text/html" rel="alternate" href="http://localhost:25001/people/1"/>
   <title>ilake</title>
   <content type="html">ilake</content>
   <books>
     <title>book123</title>
     <title>bbbb</title>
   </books>
 </entry>
 <entry>
   <id>tag:localhost,2005:User/2</id>
   <published>2008-11-09T16:39:09Z</published>
   <updated>2008-11-09T16:39:09Z</updated>
   <link type="text/html" rel="alternate" href="http://localhost:25001/people/2"/>
   <title>lake2</title>
   <content type="html">lake2</content>
   <books>
     <title>[lake2]lake 2 book</title>
   </books>
 </entry>
</feed>