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module ActionController #:nodoc:
module Caching
# Fragment caching is used for caching various blocks within
# views 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 done using
# the <tt>cache</tt> helper available in the Action View. A
# template with fragment caching might look like:
#
# <b>Hello <%= @name %></b>
#
# <% 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")
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
# 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)
end
# Writes <tt>content</tt> to the location signified by
# <tt>key</tt> (see <tt>expire_fragment</tt> for acceptable formats).
def write_fragment(key, content, options = nil)
return content unless cache_configured?
key = fragment_cache_key(key)
instrument_fragment_cache :write_fragment, key do
content = content.to_str
cache_store.write(key, content, options)
end
content
end
# Reads a cached fragment from the location signified by <tt>key</tt>
# (see <tt>expire_fragment</tt> for acceptable formats).
def read_fragment(key, options = nil)
return unless cache_configured?
key = fragment_cache_key(key)
instrument_fragment_cache :read_fragment, key do
result = cache_store.read(key, options)
result.respond_to?(:html_safe) ? result.html_safe : result
end
end
# Check if a cached fragment from the location signified by
# <tt>key</tt> exists (see <tt>expire_fragment</tt> for acceptable formats)
def fragment_exist?(key, options = nil)
return unless cache_configured?
key = fragment_cache_key(key)
instrument_fragment_cache :exist_fragment?, key do
cache_store.exist?(key, options)
end
end
# Removes fragments from the cache.
#
# +key+ can take one of three forms:
#
# * String - This would normally take the form of a path, like
# <tt>pages/45/notes</tt>.
# * Hash - Treated as an implicit call to +url_for+, like
# <tt>{:controller => "pages", :action => "notes", :id => 45}</tt>
# * Regexp - Will remove any fragment that matches, so
# <tt>%r{pages/\d*/notes}</tt> might remove all notes. Make sure you
# don't use anchors in the regex (<tt>^</tt> or <tt>$</tt>) because
# the actual filename matched looks like
# <tt>./cache/filename/path.cache</tt>. Note: Regexp expiration is
# only supported on caches that can iterate over all keys (unlike
# memcached).
#
# +options+ is passed through to the cache store's <tt>delete</tt>
# method (or <tt>delete_matched</tt>, for Regexp keys.)
def expire_fragment(key, options = nil)
return unless cache_configured?
key = fragment_cache_key(key) unless key.is_a?(Regexp)
instrument_fragment_cache :expire_fragment, key do
if key.is_a?(Regexp)
cache_store.delete_matched(key, options)
else
cache_store.delete(key, options)
end
end
end
def instrument_fragment_cache(name, key)
ActiveSupport::Notifications.instrument("#{name}.action_controller", :key => key){ yield }
end
end
end
end
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