module ActionController::ConditionalGet

def expires_in(seconds, options = {}) #:doc:

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

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

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

def expires_now #:doc:

:doc:
intermediate caches (like caching proxy servers).
Sets a HTTP 1.1 Cache-Control header of "no-cache" so no caching should occur by the browser or 
def expires_now #:doc:
  response.cache_control.replace(:no_cache => true)
end

def fresh_when(options)


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

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

Example:

* :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).
* :last_modified
* :etag
Parameters:

"304 Not Modified" response if the request is already fresh.
Sets the etag, last_modified, or both on the response and renders a 
def fresh_when(options)
  options.assert_valid_keys(:etag, :last_modified, :public)
  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

def stale?(options)

end
end
end
# all the supported formats
respond_to do |format|
@statistics = @article.really_expensive_call
if stale?(:etag => @article, :last_modified => @article.created_at.utc)

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

Example:

* :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).
* :last_modified
* :etag
Parameters:

it's fresh and we don't need to generate anything and a reply of "304 Not Modified" is sent.
request is considered stale and should be generated from scratch. Otherwise,
the client request. If the request doesn't match the options provided, the
Sets the etag and/or last_modified on the response and checks it against 
def stale?(options)
  fresh_when(options)
  !request.fresh?(response)
end