Action caching for Action Pack (removed from core in Rails 4.0).

Add this line to your application's Gemfile:

gem 'actionpack-action_caching'

And then execute:

$ bundle

Or install it yourself as:

$ gem install actionpack-action_caching

Action caching is similar to page caching by the fact that the entire output of the response is cached, but unlike page caching, every request still goes through Action Pack. The key benefit of this is that filters run before the cache is served, which allows for authentication and other restrictions on whether someone is allowed to execute such action.

class ListsController < ApplicationController
  before_action :authenticate, except: :public

  caches_page   :public
  caches_action :index, :show
end

In this example, the public action doesn't require authentication so it's possible to use the faster page caching. On the other hand index and show require authentication. They can still be cached, but we need action caching for them.

Action caching uses fragment caching internally and an around filter to do the job. The fragment cache is named according to the host and path of the request. A page that is accessed at http://david.example.com/lists/show/1 will result in a fragment named david.example.com/lists/show/1. This allows the cacher to differentiate between david.example.com/lists/ and jamis.example.com/lists/ -- which is a helpful way of assisting the subdomain-as-account-key pattern.

Different representations of the same resource, e.g. http://david.example.com/lists and http://david.example.com/lists.xml are treated like separate requests and so are cached separately. Keep in mind when expiring an action cache that action: "lists" is not the same as action: "list", format: :xml.

You can modify the default action cache path by passing a :cache_path option. This will be passed directly to ActionCachePath.new. This is handy for actions with multiple possible routes that should be cached differently. If a proc (or an object that responds to to_proc) is given, it is called with the current controller instance.

And you can also use :if (or :unless) to control when the action should be cached, similar to how you use them with before_action.

As of Rails 3.0, you can also pass :expires_in with a time interval (in seconds) to schedule expiration of the cached item.

The following example depicts some of the points made above:

class ListsController < ApplicationController
  before_action :authenticate, except: :public

  # simple fragment cache
  caches_action :current

  # expire cache after an hour
  caches_action :archived, expires_in: 1.hour

  # cache unless it's a JSON request
  caches_action :index, unless: -> { request.format.json? }

  # custom cache path
  caches_action :show, cache_path: { project: 1 }

  # custom cache path with a proc
  caches_action :history, cache_path: -> { request.domain }

  # custom cache path with a symbol
  caches_action :feed, cache_path: :user_cache_path

  protected
    def user_cache_path
      if params[:user_id]
        user_list_url(params[:user_id], params[:id])
      else
        list_url(params[:id])
      end
    end
end

If you pass layout: false, it will only cache your action content. That's useful when your layout has dynamic information.

Note: Both the :format param and the Accept header are taken into account when caching the fragment with the :format having precedence. For backwards compatibility when the Accept header indicates a HTML request the fragment is stored without the extension but if an explicit "html" is passed in :format then that is used for storing the fragment.

1. Fork it.
2. Create your feature branch (git checkout -b my-new-feature).
3. Commit your changes (git commit -am 'Add some feature').
4. Push to the branch (git push origin my-new-feature).
5. Create a new Pull Request.