Modernize the documentation for view caching somewhat

2 files changed, 23 insertions, 53 deletions

diff --git a/actionpack/lib/action_controller/caching/fragments.rb b/actionpack/lib/action_controller/caching/fragments.rb
index abeb49d16f..9c77b0ccf4 100644
--- a/actionpack/lib/action_controller/caching/fragments.rb
+++ b/actionpack/lib/action_controller/caching/fragments.rb
@@ -5,48 +5,18 @@ module ActionController #:nodoc:
     # 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 done using
-    # the <tt>cache</tt> helper available in the Action View. A 
-    # template with fragment caching might look like:
+    # the <tt>cache</tt> helper available in the Action View. See
+    # ActionView::Helpers::CacheHelper for more information.
     #
-    #   <b>Hello <%= @name %></b>
+    # While it's strongly recommended that you use key-based cache
+    # expiration (see links in CacheHelper for more information),
+    # it is also possible to manually expire caches. For example:
     #
-    #   <% cache do %>
-    #     All the topics in the system:
-    #     <%= render :partial => "topic", :collection => Topic.all %>
-    #   <% end %>
-    #
-    # This cache will bind the name of the action that called it, so if
-    # this code was part of the view for the topics/list action, you 
-    # would be able to invalidate it using:
-    #
-    #   expire_fragment(:controller => "topics", :action => "list")
-    #
-    # This default behavior is limited if you need to cache multiple 
-    # fragments per action or if the action itself is cached using 
-    # <tt>caches_action</tt>. To remedy this, there is an option to 
-    # qualify the name of the cached fragment by using the 
-    # <tt>:action_suffix</tt> option:
-    #
-    #   <% cache(:action => "list", :action_suffix => "all_topics") do %>
-    #
-    # That would result in a name such as 
-    # <tt>/topics/list/all_topics</tt>, avoiding conflicts with the 
-    # action cache and with any fragments that use a different suffix.
-    # Note that the URL doesn't have to really exist or be callable
-    # - the url_for system is just used to generate unique cache names
-    # that we can refer to when we need to expire the cache.
-    #
-    # The expiration call for this example is:
-    #
-    #   expire_fragment(:controller => "topics", 
-    #                   :action => "list", 
-    #                   :action_suffix => "all_topics")
+    #   expire_fragment("name_of_cache")
     module Fragments
       # Given a key (as described in <tt>expire_fragment</tt>), returns
       # a key suitable for use in reading, writing, or expiring a 
-      # cached fragment. If the key is a hash, the generated key is the
-      # return value of url_for on that hash (without the protocol). 
-      # All keys are prefixed with <tt>views/</tt> and uses
+      # cached fragment. All keys are prefixed with <tt>views/</tt> and uses
       # ActiveSupport::Cache.expand_cache_key for the expansion.
       def fragment_cache_key(key)
         ActiveSupport::Cache.expand_cache_key(key.is_a?(Hash) ? url_for(key).split("://").last : key, :views)
diff --git a/actionpack/lib/action_view/helpers/cache_helper.rb b/actionpack/lib/action_view/helpers/cache_helper.rb
index 33799d7d71..39518268df 100644
--- a/actionpack/lib/action_view/helpers/cache_helper.rb
+++ b/actionpack/lib/action_view/helpers/cache_helper.rb
@@ -8,28 +8,28 @@ module ActionView
       # fragments, and so on. This method takes a block that contains
       # the content you wish to cache. 
       #
-      # See ActionController::Caching::Fragments for usage instructions.
+      # The best way to use this is by doing key-based cache expiration
+      # on top of a cache store like Memcached that'll automatically
+      # kick out old entries. For more on key-based expiration, see:
+      # http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works
       #
-      # If you want to cache a navigation menu, you can do following:
+      # When using this method, you list the cache dependencies as part of
+      # the name of the cache, like so:
       #
-      #   <% cache do %>
-      #     <%= render :partial => "menu" %>
+      #   <% cache [ "v1", project ] do %>
+      #     <b>All the topics on this project</b>
+      #     <%= render project.topics %>
       #   <% end %>
       #
-      # You can also cache static content:
+      # This approach will assume that when a new topic is added, you'll touch
+      # the project. The cache key generated from this call will be something like:
       #
-      #   <% cache do %>
-      #      <p>Hello users!  Welcome to our website!</p>
-      #   <% end %>
-      #
-      # Static content with embedded ruby content can be cached as 
-      # well:
+      #   views/v1/projects/123-20120806214154
+      #            ^class   ^id ^updated_at
       #
-      #    <% cache do %>
-      #      Topics:
-      #      <%= render :partial => "topics", :collection => @topic_list %>
-      #      <i>Topics listed alphabetically</i>
-      #    <% end %>
+      # If you update the rendering of topics, you just bump the version to v2.
+      # Otherwise the cache is automatically bumped whenever the project updated_at
+      # is touched.
       def cache(name = {}, options = nil, &block)
         if controller.perform_caching
           safe_concat(fragment_for(name, options, &block))