cache devise's current_user method, speed up page's load, used for guanxi_cms, Suitable for devise 2.x - 3.x, Rails 3.x

user_observer.rb

class UserObserver < Mongoid::Observer

  def after_save(record)
    expire_cache(record)
  end

  private
  def expire_cache(record)
    Rails.cache.delete("user:#{record.id}")
  end
end

userable.rb

# encoding: UTF-8
module Userable
  extend ActiveSupport::Concern

  included do
    # super devise's `serialize_from_session`, which can cache current_user in session
    # Suitable for devise 2.x - 3.x
    # https://github.com/plataformatec/devise/blob/master/lib/devise/models/authenticatable.rb#L207
    def self.serialize_from_session(key, salt)
      single_key = key.is_a?(Array) ? key.first : key
      record = Rails.cache.fetch("user:#{single_key}") { self.where(id: single_key).limit(1).first }
      record if record && record.authenticatable_salt == salt
      record.blank? ? super : record
    end
  end

  # instance method
end