module ActionController::ConditionalGet

def combine_etags(options)
  etags = etaggers.map { |etagger| instance_exec(options, &etagger) }.compact
  etags.unshift options[:etag]
end

The method will also ensure a HTTP Date header for client compatibility.

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, public: true, must_revalidate: true
expires_in 3.hours, public: true
expires_in 20.minutes

instruction, so that intermediate caches must not cache the response.
Sets a HTTP 1.1 Cache-Control header. Defaults to issuing a +private+

def expires_in(seconds, options = {})
  response.cache_control.merge!(
    :max_age         => seconds,
    :public          => options.delete(:public),
    :must_revalidate => options.delete(:must_revalidate)
  )
  options.delete(:private)
  response.cache_control[:extras] = options.map {|k,v| "#{k}=#{v}"}
  response.date = Time.now unless response.date?
end

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

def expires_now
  response.cache_control.replace(:no_cache => true)
end

before_action { fresh_when @article, template: 'widgets/show' }

style, you can indicate which digest to include in the ETag:
When rendering a different template than the default controller/action

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

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

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

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

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

=== Example:

to skip any attempt to check for a template digest.
doesn't render a template at all, you can pass template: false
different template, you can include its digest instead. If the action
controller/action is included in ETags. If the action renders a
* :template By default, the template digest for the current
+true+ if you want your application to be cachable by other devices (proxy caches).
* :public By default the Cache-Control header is private, set this to
* :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(record_or_options, additional_options = {})
  if record_or_options.is_a? Hash
    options = record_or_options
    options.assert_valid_keys(:etag, :last_modified, :public, :template)
  else
    record  = record_or_options
    options = { etag: record, last_modified: record.try(:updated_at) }.merge!(additional_options)
  end
  response.etag          = combine_etags(options)   if options[:etag] || options[:template]
  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

end
super if stale? @article, template: 'widgets/show'
def show

style, you can indicate which digest to include in the ETag:
When rendering a different template than the default controller/action

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

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

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

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

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

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

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)

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

=== Example:

to skip any attempt to check for a template digest.
doesn't render a template at all, you can pass template: false
different template, you can include its digest instead. If the action
controller/action is included in ETags. If the action renders a
* :template By default, the template digest for the current
+true+ if you want your application to be cachable by other devices (proxy caches).
* :public By default the Cache-Control header is private, set this to
* :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?(record_or_options, additional_options = {})
  fresh_when(record_or_options, additional_options)
  !request.fresh?(response)
end