module Responders::HttpCacheResponder

Set HTTP Last-Modified headers based on the given resource. It's used only on API behavior (to_format) and is useful for a client to check in the server if a resource changed after a specific date or not.

This is not usually not used in html requests because pages contains a lot information besides the resource information, as current_user, flash messages, widgets… that are better handled with other strategies, as fragment caches and the digest of the body.

Public Class Methods

new(controller, resources, options = {}) click to toggle source
Calls superclass method
# File lib/responders/http_cache_responder.rb, line 13
def initialize(controller, resources, options = {})
  super
  @http_cache = options.delete(:http_cache)
end

Public Instance Methods

to_format() click to toggle source
Calls superclass method
# File lib/responders/http_cache_responder.rb, line 18
def to_format
  return if do_http_cache? && do_http_cache!
  super
end

Protected Instance Methods

do_http_cache!() click to toggle source
# File lib/responders/http_cache_responder.rb, line 25
def do_http_cache!
  timestamp = resources.map do |resource|
    resource.updated_at.try(:utc) if resource.respond_to?(:updated_at)
  end.compact.max

  controller.response.last_modified ||= timestamp if timestamp

  head :not_modified if fresh = request.fresh?(controller.response)
  fresh
end
do_http_cache?() click to toggle source
# File lib/responders/http_cache_responder.rb, line 36
def do_http_cache?
  get? && @http_cache != false && ActionController::Base.perform_caching &&
    persisted? && resource.respond_to?(:updated_at)
end
persisted?() click to toggle source
# File lib/responders/http_cache_responder.rb, line 41
def persisted?
  resource.respond_to?(:persisted?) ? resource.persisted? : true
end