Rails and Memcache with Dalli. How to refresh the cache just after updating or destroying it (force)

gistfile1.rb

class Contact < ActiveRecord::Base
  after_save    :expire_contact_all_cache
  after_destroy :expire_contact_all_cache

  def self.all_cached
    Rails.cache.fetch('Contact.all') { all }
  end

  def expire_contact_all_cache
    Rails.cache.fetch('Contact.all', :force => true)  do
      results = Contact.all
    end
  end
end