A simple fragment caching example in Rails 3

my_model.rb

class Conversation
  #...

  after_create :expire_dash_cache

  def add_new_comments(comments)
    # Do stuff w/ the new comments...

    save
    expire_dash_cache
  end

  def expire_dash_cache
    ActionController::Base.new.expire_fragment("dashboard_#{site.id}")
  end
end

view.html.erb

<% cache("dashboard_#{current_site.id}") do %>
  <%= render :partial => 'dashboard/conversation_table' %>
<% end %>