#en el controllador channels > index
<%= link_to_remote(image_tag('expand.png', :class => "expander", :align => "middle"), :url => {:action => 'magick_playlist'} )%>

#tambien en el controllador channels > index
<div id="playlist">
   <%= render :partial => 'channel_playlists', :collection => @channels %>
</div>

#en el partial channel_playlists

<% for playlist in @channels.playlists do %>
  <ul id="site-map" style="position: relative;">
        <li id="page_<%= playlist.id%>" class="node level-1 no-children">
          <div class="page">
            <span class="w1">
              <%= image_tag('page.png', :class => "icon", :align => "middle")%>
              <span class="title">
                Playlist <%= playlist.name %>
              </span>
            </span>
          </div>
        </li>
  </ul>
<% end %>

#Error
undefined method `playlists' for #<Array:0x48a3348>