module AbstractController::Caching::Fragments
Abstract Controller Caching Fragments
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. See ActionView::Helpers::CacheHelper
for more information.
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:
expire_fragment('name_of_cache')
Public instance methods
Given a key (as described in expire_fragment
), returns a key array suitable for use in reading, writing, or expiring a cached fragment. All keys begin with :views
, followed by ENV["RAILS_CACHE_ID"]
or ENV["RAILS_APP_VERSION"]
if set, followed by any controller-wide key prefix values, ending with the specified key
value.
Source code GitHub
# File actionpack/lib/abstract_controller/caching/fragments.rb, line 68
def combined_fragment_cache_key(key)
head = self.class.fragment_cache_keys.map { |k| instance_exec(&k) }
tail = key.is_a?(Hash) ? url_for(key).split("://").last : key
cache_key = [:views, ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"], head, tail]
cache_key.flatten!(1)
cache_key.compact!
cache_key
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).
Source code GitHub
# File actionpack/lib/abstract_controller/caching/fragments.rb, line 131
def expire_fragment(key, options = nil)
return unless cache_configured?
key = combined_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
Check if a cached fragment from the location signified by key
exists (see expire_fragment
for acceptable formats).
Source code GitHub
# File actionpack/lib/abstract_controller/caching/fragments.rb, line 105
def fragment_exist?(key, options = nil)
return unless cache_configured?
key = combined_fragment_cache_key(key)
instrument_fragment_cache :exist_fragment?, key do
cache_store.exist?(key, options)
end
end
Reads a cached fragment from the location signified by key
(see expire_fragment
for acceptable formats).
Source code GitHub
# File actionpack/lib/abstract_controller/caching/fragments.rb, line 93
def read_fragment(key, options = nil)
return unless cache_configured?
key = combined_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
Writes content
to the location signified by key
(see expire_fragment
for acceptable formats).
Source code GitHub
# File actionpack/lib/abstract_controller/caching/fragments.rb, line 80
def write_fragment(key, content, options = nil)
return content unless cache_configured?
key = combined_fragment_cache_key(key)
instrument_fragment_cache :write_fragment, key do
content = content.to_str
cache_store.write(key, content, options)
end
content
end