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Modernize the documentation for view caching somewhat

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commit 4154bf012d2bec2aae79e4a49aa94a70d3e91d49 1 parent 5d15287
@dhh dhh authored
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44 actionpack/lib/action_controller/caching/fragments.rb
@@ -5,48 +5,18 @@ module Caching
# 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)
View
32 actionpack/lib/action_view/helpers/cache_helper.rb
@@ -8,28 +8,28 @@ module CacheHelper
# 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))

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