Rails%203%20In%20Action

Page and action caching
Alternatively, pass a constant
Rather than passing the symbolized version of the name along to the cache_sweeper
method, you can also alternatively pass along a class:
cache_sweeper TicketsSweeeper
This doesn’t perform any differently than passing in a symbol, but is really helpful if
your sweeper was modularized:
cache_sweeper Ticketee::TicketsSweeper
You can’t pass a modularized sweeper name as a symbol, and so the
cache_sweeper method supports passing both a symbol and a constant reference
as well.
sweeper and its brethren to live. 10 In this directory you’ll create a new file called app/
sweepers/tickets_sweeper.rb and fill it with this content:
class TicketsSweeper < ActionController::Caching::Sweeper
observe Ticket
def after_create(ticket)
# expire fragment code goes here
end
end
You’ll get around to adding the expire fragment code in just a bit, but first a bit of
explanation is needed. A sweeper looks and acts much the same as an observer. By
calling the observe method at the top of the TicketsSweeper, you tell this sweeper to
watch the Ticket class for changes. The after_create method here will be called
after creation of a new Ticket object, but because you’re in a sweeper, you’ll have
access to the controller’s parameters also. With them, you can use what’s usually available
in the controller to expire the cached fragments.
To do this, you can call the expire_fragment method, passing it a regular expression.
This regular expression will match all cached fragments for the ticket’s project
for all users, effectively wiping clean the slate for this project in terms of cached pages.
Inside your after_create method you’ll put this:
expire_fragment(/projects\/#{ticket.project.id}\/.*?/)
Now when you create a new ticket for a project, this expire_fragment method will be
called. Let’s try this out now, creating a new ticket by clicking the New Ticket link on a
project’s page and filling out the form. Once you’ve clicked the Create Ticket button
on the form, you’ll see this in the console:
Expire fragment (?-mix:projects\/1\/.*?) (327.3ms)
Rails has gone through and expired all the fragments associated with this ticket’s project.
If you now go into tmp/cache and into any one of the directories there looking
10 Because it doesn’t really belong in the controllers, helpers, models, observers, or views directory, but is still a
vital part of your application.
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