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ActionController::ConditionalGet

Public Instance Methods

expires_in(seconds, options = {}) click to toggle source

Sets a HTTP 1.1 Cache-Control header. Defaults to issuing a “private” instruction, so that intermediate caches shouldn’t cache the response.

Examples:

  expires_in 20.minutes
  expires_in 3.hours, :public => true
  expires in 3.hours, 'max-stale' => 5.hours, :public => true

This method will overwrite an existing Cache-Control header. See www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.

    # File lib/action_controller/metal/conditional_get.rb, line 73
73:     def expires_in(seconds, options = {}) #:doc:
74:       response.cache_control.merge!(:max_age => seconds, :public => options.delete(:public))
75:       options.delete(:private)
76: 
77:       response.cache_control[:extras] = options.map {|k,v| "#{k}=#{v}"}
78:     end
expires_now() click to toggle source

Sets a HTTP 1.1 Cache-Control header of “no-cache” so no caching should occur by the browser or intermediate caches (like caching proxy servers).

    # File lib/action_controller/metal/conditional_get.rb, line 82
82:     def expires_now #:doc:
83:       response.cache_control.replace(:no_cache => true)
84:     end
fresh_when(options) click to toggle source

Sets the etag, last_modified, or both on the response and renders a “304 Not Modified” response if the request is already fresh.

Parameters:

  • :etag

  • :last_modified

  • :public By default the Cache-Control header is private, set this to true if you want your application to be cachable by other devices (proxy caches).

Example:

  def show
    @article = Article.find(params[:id])
    fresh_when(:etag => @article, :last_modified => @article.created_at.utc, :public => true)
  end

This will render the show template if the request isn’t sending a matching etag or If-Modified-Since header and just a “304 Not Modified” response if there’s a match.

    # File lib/action_controller/metal/conditional_get.rb, line 26
26:     def fresh_when(options)
27:       options.assert_valid_keys(:etag, :last_modified, :public)
28: 
29:       response.etag          = options[:etag]          if options[:etag]
30:       response.last_modified = options[:last_modified] if options[:last_modified]
31:       response.cache_control[:public] = true if options[:public]
32: 
33:       head :not_modified if request.fresh?(response)
34:     end
stale?(options) click to toggle source

Sets the etag and/or last_modified on the response and checks it against the client request. If the request doesn’t match the options provided, the request is considered stale and should be generated from scratch. Otherwise, it’s fresh and we don’t need to generate anything and a reply of “304 Not Modified” is sent.

Parameters:

  • :etag

  • :last_modified

  • :public By default the Cache-Control header is private, set this to true if you want your application to be cachable by other devices (proxy caches).

Example:

  def show
    @article = Article.find(params[:id])

    if stale?(:etag => @article, :last_modified => @article.created_at.utc)
      @statistics = @article.really_expensive_call
      respond_to do |format|
        # all the supported formats
      end
    end
  end
    # File lib/action_controller/metal/conditional_get.rb, line 58
58:     def stale?(options)
59:       fresh_when(options)
60:       !request.fresh?(response)
61:     end

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