对于Rails 3，将文章中给出的说明与@science 的答案不同.在您的 environments/development.rb 文件中，添加以下行:

For Rails 3, vary the instructions given in the article from @science's answer. In your environments/development.rb file, add the lines:

ActiveSupport::Dependencies.autoload_paths << File::join( Rails.root, 'lib')
ActiveSupport::Dependencies.explicitly_unloadable_constants << 'MyModuleInLibFolder'

当然，用您的模块名称替换 MyModuleInLibFolder.

Of course, substitute the name of your module for MyModuleInLibFolder.