在 Rails 3 升级后，安装插件时获得 nil:NilClass 的未定义方法“root”答案

【问题标题】：After Rails 3 upgrade getting undefined method `root' for nil:NilClass when installing plugins在 Rails 3 升级后，安装插件时获得 nil:NilClass 的未定义方法“root”
【发布时间】：2011-11-19 15:03:38
【问题描述】：

我正在使用 rails_upgrade 插件将我的应用程序从 Rails 2.3.14 移动到 Rails 3.0.11。我已经备份并运行 rails new 。在我的应用程序目录中并让服务器启动。一切似乎都可以继续进行，但是当我尝试安装新插件时出现错误：

nil:NilClass 的未定义方法 `root'

这是堆栈跟踪。

    1.9.2 v@Feather ⚡ rails plugin install https://github.com/rails/rails_upgrade.git
    /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/whiny_nil.rb:48:in `method_missing': undefined method `root' for nil:NilClass (NoMethodError)
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.11/lib/rails/commands/plugin.rb:282:in `initialize'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.11/lib/rails/commands/plugin.rb:352:in `new'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.11/lib/rails/commands/plugin.rb:352:in `parse!'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.11/lib/rails/commands/plugin.rb:547:in `<top (required)>'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `require'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `block in require'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:593:in `new_constants_in'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:225:in `load_dependency'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.11/lib/active_support/dependencies.rb:239:in `require'
from /Users/vince/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.11/lib/rails/commands.rb:17:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

看起来罪魁祸首是这一行：@rails_root = RailsEnvironment.default.root

【问题讨论】：

标签： ruby-on-rails-3 ruby-on-rails-plugins

【解决方案1】：

奇怪，终于明白了。原来是我的 Gemfile 中的 slim_scooge gem 导致了这个问题。将它从我的捆绑包中删除，一切都很好。晦涩难懂的问题，但希望以后可以节省其他人的时间。

【讨论】：