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<title>Module: ActionController::Caching::Sweeping</title>
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<td><strong>Module</strong></td>
<td class="class-name-in-header">ActionController::Caching::Sweeping</td>
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<td><strong>In:</strong></td>
<td>
<a href="../../../files/lib/action_controller/caching/sweeping_rb.html">
lib/action_controller/caching/sweeping.rb
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<p>
Sweepers are the terminators of the caching world and responsible for
expiring caches when model objects change. They do this by being
half-observers, half-filters and implementing callbacks for both roles. A
Sweeper example:
</p>
<pre>
class ListSweeper < ActionController::Caching::Sweeper
observe List, Item
def after_save(record)
list = record.is_a?(List) ? record : record.list
expire_page(:controller => "lists", :action => %w( show public feed ), :id => list.id)
expire_action(:controller => "lists", :action => "all")
list.shares.each { |share| expire_page(:controller => "lists", :action => "show", :id => share.url_key) }
end
end
</pre>
<p>
The sweeper is assigned in the controllers that wish to have its job
performed using the <tt>cache_sweeper</tt> class method:
</p>
<pre>
class ListsController < ApplicationController
caches_action :index, :show, :public, :feed
cache_sweeper :list_sweeper, :only => [ :edit, :destroy, :share ]
end
</pre>
<p>
In the example above, four actions are cached and three actions are
responsible for expiring those caches.
</p>
<p>
You can also name an explicit class in the declaration of a sweeper, which
is needed if the sweeper is in a module:
</p>
<pre>
class ListsController < ApplicationController
caches_action :index, :show, :public, :feed
cache_sweeper OpenBar::Sweeper, :only => [ :edit, :destroy, :share ]
end
</pre>
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