ruby-on-rails-3 - 我不能用 redis-store 跟踪 s

Question

我的轨道是 3.2.8

我有像下面这样的宝石

#gemfile
gem 'redis', '3.0.2'
gem 'redis-store', '1.1.3'
gem 'redis-rails'

#session_store.rb
Application.config.session_store :redis_session_store

然后是轨道

它报告如下错误

=> Booting Thin
=> Rails 3.2.8 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/Users/magicstudio/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.8/lib/rails/application/configuration.rb:140:in `const_get': uninitialized constant ActionDispatch::Session::RedisSessionStore (NameError)
    from /Users/magicstudio/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.8/lib/rails/application/configuration.rb:140:in `session_store'

为什么？