问题是Rails期望模块中的控制器称为 Users ，因为这就是 namespace：user 的推断。也许您是想使用 scope 而不是 namespace ？

The problem is that Rails is expecting there to be a controller within a module called Users because that's what namespace :user infers. Perhaps you meant to use scope instead of namespace?

scope :path => "user" do
  root :to => "users#profile"
end

注意：在这种情况下，如果您只有一种方法，使用 scope 并不明智，但是如果您有多个带有 / user 前缀的那么就可以了如果您只有一个，我会改为：

Note: in this situation if you've only got one route it would not be wise to use scope, but if you've got multiple ones with the /user prefix then it would be fine to. If you only had one, I would do this instead:

get '/user', :to => "users#profile"