这些行实际上并不会改变资产的使用方式。

These lines don't actually change how your assets are used.

第一行，

Bundler.require *Rails.groups(:assets => %w(development test))

仅在开发和测试环境中从资产组中加载宝石。这意味着 sass-rails 和 uglifier 之类的产品将无法在生产中使用，这意味着您赢得了如果您正在使用这些宝石，就无法正确地在生产中即时编译/最小化/无论您使用什么资产。

only loads gems from the assets group in your development and test environment. This means that things like sass-rails and uglifier won't be available in production, which then means that you won't be able to properly compile/minify/whatever your assets on the fly in production if you're making use of those gems.

另一方面，

Bundler.require(:default, :assets, Rails.env)

将在任何环境中加载资产组，使这些宝石可用于生产中以进行资产编译/缩小/

will load the assets group in any environment, making those gems available in production to do asset compilation/minification/whatever on the fly.

因此，如上所述，这些行实际上并没有改变资产管道的行为-它只是意味着您应该使用第一个if您将要对资产进行预编译以进行生产，或者如果您要在生产中懒散地进行编译，则使用第二个资产。

So, as stated above, these lines don't actually change the behaviour of your asset pipeline - it simply means that you should use the first if you're going to precompile your assets for production, or use the second if you're going to lazily compile in production.