# module 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 must not 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 118
    def expires_in(seconds, options = {}) #:doc:
      response.cache_control.merge!(:max_age => seconds, :public => options.delete(:public))
      options.delete(:private)

      response.cache_control[:extras] = options.map {|k,v| "#{k}=#{v}"}
    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 127
    def expires_now #:doc:
      response.cache_control.replace(:no_cache => true)
    end

fresh_when(record_or_options, additional_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, :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.

You can also just pass a record where last_modified will be set by calling updated_at and the etag by passing the object itself. Example:

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

When passing a record, you can still set whether the public header:

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

    # File lib/action_controller/metal/conditional_get.rb, line 39
    def fresh_when(record_or_options, additional_options = {})
      if record_or_options.is_a? Hash
        options = record_or_options
        options.assert_valid_keys(:etag, :last_modified, :public)
      else
        record  = record_or_options
        options = { :etag => record, :last_modified => record.try(:updated_at) }.merge(additional_options)
      end

      response.etag          = options[:etag]          if options[:etag]
      response.last_modified = options[:last_modified] if options[:last_modified]
      response.cache_control[:public] = true if options[:public]

      head :not_modified if request.fresh?(response)
    end

stale?(record_or_options, additional_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)
        @statistics = @article.really_expensive_call
        respond_to do |format|
          # all the supported formats
        end
      end
    end

You can also just pass a record where last_modified will be set by calling updated_at and the etag by passing the object itself. Example:

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

      if stale?(@article)
        @statistics = @article.really_expensive_call
        respond_to do |format|
          # all the supported formats
        end
      end
    end

When passing a record, you can still set whether the public header:

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

      if stale?(@article, :public => true)
        @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 103
    def stale?(record_or_options, additional_options = {})
      fresh_when(record_or_options, additional_options)
      !request.fresh?(response)
    end