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我在Rails 4應用程序中對幾個視圖做了一些小的更改，並將我的獨角獸gem移動到我的Gemfile的主要部分，啓動了服務器，並在<%= csrf_meta_tags %>行上以下面的右邊迎接：未初始化的常量REXMLUtiliyNodeString
uninitialized constant REXMLUtiliyNodeString
跆拳道，夥計？
我的谷歌搜索並沒有引導我太多。約有9個結果，與REXMLUtiliyNodeString類無關。當我搜索REXMLUtiliyNodeString時，結果也是相同的。我想評論的csrf_meta_tags出來看發生了什麼，我的服務器給我一個包含查詢字符串，下一個表單等
我使用better_errors寶石，下一個環節上同樣的錯誤，當我看着在值時，它表明：
Session expired
>> undefined
有道理，爲什麼csrf_meta_tags是給了我一個問題，但我不明白爲什麼會過期。也許我的一些服務器日誌會有所幫助。這是直到模板渲染的東西：
Completed 500 Internal Server Error in 18ms
NameError - uninitialized constant REXMLUtiliyNodeString:
activesupport (4.0.0) lib/active_support/dependencies.rb:500:in `load_missing_constant'
activesupport (4.0.0) lib/active_support/dependencies.rb:183:in `const_missing'
rspec-core (2.14.5) lib/rspec/core/backward_compatibility.rb:14:in `const_missing'
activesupport (4.0.0) lib/active_support/inflector/methods.rb:226:in `block in constantize'
activesupport (4.0.0) lib/active_support/inflector/methods.rb:224:in `constantize'
activesupport (4.0.0) lib/active_support/core_ext/string/inflections.rb:66:in `constantize'
activesupport (4.0.0) lib/active_support/core_ext/marshal.rb:10:in `rescue in load_with_autoloading'
activesupport (4.0.0) lib/active_support/core_ext/marshal.rb:6:in `load_with_autoloading'
activesupport (4.0.0) lib/active_support/message_encryptor.rb:93:in `_decrypt'
activesupport (4.0.0) lib/active_support/message_encryptor.rb:63:in `decrypt_and_verify'
actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:461:in `decrypt_and_verify'
actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:476:in `[]'
actionpack (4.0.0) lib/action_dispatch/middleware/session/cookie_store.rb:113:in `get_cookie'
actionpack (4.0.0) lib/action_dispatch/middleware/session/cookie_store.rb:89:in `block in unpacked_cookie_data'
actionpack (4.0.0) lib/action_dispatch/middleware/session/abstract_store.rb:51:in `stale_session_check!'
actionpack (4.0.0) lib/action_dispatch/middleware/session/cookie_store.rb:88:in `unpacked_cookie_data'
actionpack (4.0.0) lib/action_dispatch/middleware/session/cookie_store.rb:82:in `block in extract_session_id'
actionpack (4.0.0) lib/action_dispatch/middleware/session/abstract_store.rb:51:in `stale_session_check!'
actionpack (4.0.0) lib/action_dispatch/middleware/session/cookie_store.rb:81:in `extract_session_id'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:46:in `block in []'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:45:in `[]'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:67:in `id'
rack (1.5.2) lib/rack/session/abstract/id.rb:282:in `current_session_id'
rack (1.5.2) lib/rack/session/abstract/id.rb:288:in `session_exists?'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:140:in `exists?'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:160:in `load_for_read!'
actionpack (4.0.0) lib/action_dispatch/request/session.rb:86:in `[]'
actionpack (4.0.0) lib/action_controller/metal/request_forgery_protection.rb:194:in `form_authenticity_token'
actionpack (4.0.0) lib/abstract_controller/helpers.rb:53:in `form_authenticity_token'
actionpack (4.0.0) lib/action_view/helpers/csrf_helper.rb:21:in `csrf_meta_tags'
app/views/layouts/application.html.erb:8:in `_app_views_layouts_application_html_erb___1806160678256643230_70323633825000'
actionpack (4.0.0) lib/action_view/template.rb:143:in `block in render'
任何人都可以請幫我指出了正確的方向，即使你不知道答案嗎？我百分之百難過，今天我需要推出一些改變。
謝謝！