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module ActionView
# = Action View Cache Helper
module Helpers
module CacheHelper
# This helper exposes a method for caching fragments of a view
# rather than an entire action or page. This technique is useful
# caching pieces like menus, lists of newstopics, static HTML
# fragments, and so on. This method takes a block that contains
# the content you wish to cache.
#
# 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
#
# When using this method, you list the cache dependencies as part of
# the name of the cache, like so:
#
# <% cache [ "v1", project ] do %>
# <b>All the topics on this project</b>
# <%= render project.topics %>
# <% end %>
#
# 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:
#
# views/v1/projects/123-20120806214154
# ^class ^id ^updated_at
#
# 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))
else
yield
end
nil
end
private
# TODO: Create an object that has caching read/write on it
def fragment_for(name = {}, options = nil, &block) #:nodoc:
if fragment = controller.read_fragment(name, options)
fragment
else
# VIEW TODO: Make #capture usable outside of ERB
# This dance is needed because Builder can't use capture
pos = output_buffer.length
yield
output_safe = output_buffer.html_safe?
fragment = output_buffer.slice!(pos..-1)
if output_safe
self.output_buffer = output_buffer.class.new(output_buffer)
end
controller.write_fragment(name, fragment, options)
end
end
end
end
end
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