Fragment caching is used for caching various blocks within
templates without caching the entire action as a whole. This is
useful when certain elements of an action change frequently or
depend on complicated state while other parts rarely change or
can be shared amongst multiple parties. The caching is doing
using the cache helper available in the Action View. A template
with caching might look something like: <b>Hello <%= @name
%></b> <% cache do %> All the topics in the system: <%=
render_collection_of_partials "topic", Topic.find_all %> <% end
%> This cache will bind to the name of action that called it. So
you would be able to invalidate it using
expire_fragment(:controller => "topics", :action => "list") — if
that was the controller/action used. This is not too helpful if
you need to cache multiple fragments per action or if the action
itself is cached using caches_action. So instead we should
qualify the name of the action used with something like: <%
cache(:action => "list", :action_suffix => "all_topi