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 cache helper available in the Action View. A # template with fragment caching might look like: # # Hello <%= @name %> # # <% cache do %> # All the topics in the system: # <%= render :partial => "topic", :collection => Topic.find(: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 # caches_action. To remedy this, there is an option to # qualify the name of the cached fragment by using the # :action_suffix option: # # <% cache(:action => "list", :action_suffix => "all_topics") do %> # # That would result in a name such as # /topics/list/all_topics, 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 expire_fragment), 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 views/ 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 content to the location signified by # key (see expire_fragment 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.html_safe.to_str if content.respond_to?(:html_safe) cache_store.write(key, content, options) end content end # Reads a cached fragment from the location signified by key # (see expire_fragment 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 # key exists (see expire_fragment 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 # pages/45/notes. # * Hash - Treated as an implicit call to +url_for+, like # {:controller => "pages", :action => "notes", :id => 45} # * Regexp - Will remove any fragment that matches, so # %r{pages/\d*/notes} might remove all notes. Make sure you # don't use anchors in the regex (^ or $) because # the actual filename matched looks like # ./cache/filename/path.cache. 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 delete # method (or delete_matched, for Regexp keys.) def expire_fragment(key, options = nil) return unless cache_configured? key = fragment_cache_key(key) unless key.is_a?(Regexp) message = nil 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