Scala自我注释类型

Question

阅读这篇精彩的文章

http://www.cakesolutions.net/teamblogs/2011/12/19/cake-pattern-in-depth

关于自我类型注释，我想知道当我在

中使用self或某个任意名称时会有什么区别

this: UserRepositoryComponent =>

或

self: UserRepositoryComponent =>

或

user: UserRepositoryComponent => 

针对：

trait DefaultUserServiceComponent extends UserServiceComponent {
      this: UserRepositoryComponent =>

      def userService = new DefaultUserService

      class DefaultUserService extends UserService {
        def findAll = userLocator.findAll

        def save(user: User) {
          userUpdater.save(user: User)
        }
      }
    }