Module | ActionController::Caching::Sweeping
In: | lib/action_controller/caching/sweeping.rb

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:

      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

The sweeper is assigned in the controllers that wish to have its job performed using the `cache_sweeper` class method:

      class ListsController < ApplicationController
        caches_action :index, :show, :public, :feed
        cache_sweeper :list_sweeper, :only => [ :edit, :destroy, :share ]
      end

In the example above, four actions are cached and three actions are responsible for expiring those caches.

You can also name an explicit class in the declaration of a sweeper, which is needed if the sweeper is in a module:

      class ListsController < ApplicationController
        caches_action :index, :show, :public, :feed
        cache_sweeper OpenBar::Sweeper, :only => [ :edit, :destroy, :share ]
      end

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