module ActionController #:nodoc: module Caching # 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 done using the cache helper available in the Action View. A template with caching might look something like: # # Hello <%= @name %> # <% cache do %> # All the topics in the system: # <%= render :partial => "topic", :collection => Topic.find(:all) %> # <% end %> # # This cache will bind to 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 of limited use if you need to cache multiple fragments per action or if the action itself is cached using # caches_action, so we also have the option to qualify the name of the cached fragment with something like: # # <% 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 def fragment_for(buffer, name = {}, options = nil, &block) #:nodoc: if perform_caching if fragment_exist?(name,options) buffer.concat(read_fragment(name, options)) else pos = buffer.length block.call write_fragment(name, buffer[pos..-1], options) end else block.call end 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 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 cache_store.read(key, options) 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("action_controller.#{name}", :key => key){ yield } end end end end