如何将 Rails 升级到 4.2?

How to Upgrade Rails to 4.2?

我想将我的 Rails 应用程序从 3.2.12 正确升级到 4.2 ...

有人发给我这个 link: http://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html

目前我正在尝试从 3.2.12 升级到 4.0 ...我挂在第 5.4 步:

Rails 4.0 no longer supports loading plugins from vendor/plugins. 
You must replace any plugins by extracting them to gems and adding them to your Gemfile. 
If you choose not to make them gems, you can move them into, say, lib/my_plugin/* 
and add an appropriate initializer in config/initializers/my_plugin.rb.

好的,从 vendor/plugins 复制到 lib 没问题...但是我必须如何设置初始值设定项? ...

初始化器是在启动时执行的纯 ruby 文件。他们住在config/initializers