module ActionController::ConditionalGet

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

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

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

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

# File actionpack/lib/action_controller/metal/conditional_get.rb, line 152
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

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 actionpack/lib/action_controller/metal/conditional_get.rb, line 166
def expires_now
  response.cache_control.replace(:no_cache => true)
end

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.

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 actionpack/lib/action_controller/metal/conditional_get.rb, line 69
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          = combine_etags(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

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.

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 actionpack/lib/action_controller/metal/conditional_get.rb, line 136
def stale?(record_or_options, additional_options = {})
  fresh_when(record_or_options, additional_options)
  !request.fresh?(response)
end