Rails Bookmark app似乎无法识别Devise gem方法？

Question

我正在进行此截屏演练：http://andreapavoni.com/blog/2013/8/a-rails-4-tutorial-application-for-beginners/#.U9EkF7FouwU

似乎程序没有识别Devise方法，我已经对它进行了两次捆绑安装。

以下是错误消息：

<pre>
undefined method `devise_for' for #<ActionDispatch::Routing::Mapper:0x3fb2230>
Extracted source (around line #3):

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Rails.application.routes.draw do
# Devise was getting an error message, devise_for method
devise_for :users
resources :bookmarks
# The priority is based upon order of creation: first created -> highest priority.

Rails.root: C:/Sites/rubystuff/bookmarks
Application Trace | Framework Trace | Full Trace

config/routes.rb:3:in `block in <top (required)>'
config/routes.rb:1:in `<top (required)>'

This error occurred while loading the following files:
   C:/Sites/rubystuff/bookmarks/config/routes.rb

<code>

我的配置/路由/ .rb

<pre>
    Rails.application.routes.draw do
    # Devise was getting an error message, devise_for method
    devise_for :users 
    resources :bookmarks

    # The priority is based upon order of creation: first created -> highest priority.
    # See how all your routes lay out with "rake routes".

    # You can have the root of your site routed with "root"

    root 'bookmarks#index'


end 
<code>

我使用的是rails 4.1.1和ruby 1.9.3。非常感谢你的帮助。