1  atom_feed(:url => formatted_posts_url(:atom)) do |feed|
   2    feed.title(@category.name)
   3    feed.updated(@posts.first ? @posts.first.created_at : Time.now.utc)
   4  
   5    for post in @posts
   6      feed.entry(post) do |entry|
   7        entry.title(post.title)
   8        entry.content(post.body_html, :type => 'html')
   9        entry.updated post.updated_at
  10  
  11        for tag in post.tags
  12          entry.category :term => url_for(tag), :label => tag.name
  13        end
  14      end
  15    end
  16  end

This here is a quick-and-dirty implementation of folders for jQuery:

Markup

Any markup following the naming conventions should work, for example:

   1  <ul class="collapsible">
   2    <li>
   3       <a href="" class="toggle-button">This be the folder</a>
   4      <ul style="display:none" class="collapsible-content">
   5          <li>This be the folder content</li>
   6          <li>This be the folder content</li>
   7      </ul>
   8    </li>
   9  </ul>

JavaScript

   1  /**
   2   * Collapsible categories implementation.
   3   * 
   4   */
   5  var category = {
   6    find_category: function(target) {
   7      var category = target;
   8      // This isn't the category, so look for it
   9      if(!target.hasClass('collapsible')) {
  10        category = target.closest('.collapsible');
  11      }
  12      return category;
  13    },
  14    collapse: function(target) {
  15      var category = this.find_category(target);
  16      category.find('.collapsible-content').hide();
  17      category.removeClass('expanded');
  18      category.addClass('collapsed');
  19    },
  20    expand: function(target) {
  21      var category = this.find_category(target);
  22      category.find('.collapsible-content').show();
  23      category.addClass('expanded');
  24      category.removeClass('collapsed');
  25    },
  26    toggle: function(target) {
  27      var category = this.find_category(target);
  28  
  29      var is_expanded = category.hasClass('expanded');
  30  
  31      if(is_expanded) {
  32        this.collapse(category);
  33      } else {
  34        this.expand(category);
  35      }
  36    }
  37  }

Usage

   1  $('.toggle-button').live('click', function() {
   2    category.toggle($(this));
   3    return false;
   4  });

The model:

   1  class Category
   2  ...
   3    def recurse
   4      yield(self)
   5  
   6      children.each do |child|
   7        child.recurse {|sibling| yield sibling}
   8      end
   9    end
  10  end

The recusion:

   1  Category.root.recurse do |child|
   2    puts child
   3  end