为什么使用scala的蛋糕模式而不是抽象字段？

给定在Programming Scala中的示例TwitterClientComponent使用蛋糕模式声明这样的依赖关系：

//other trait declarations elided for clarity
...

trait TwitterClientComponent {

  self: TwitterClientUIComponent with
        TwitterLocalCacheComponent with
        TwitterServiceComponent =>

  val client: TwitterClient

  class TwitterClient(val user: TwitterUserProfile) extends Tweeter {
    def tweet(msg: String) = {
      val twt = new Tweet(user,msg,new Date)
      if (service.sendTweet(twt)) {
        localCache.saveTweet(twt)
        ui.showTweet(twt)
      }
    }
  }
}

这是如何更好地声明依赖关系作为抽象字段如下？

trait TwitterClient(val user: TwitterUserProfile) extends Tweeter {
  //abstract fields instead of cake pattern self types
  val service: TwitterService
  val localCache: TwitterLocalCache
  val ui: TwitterClientUI

  def tweet(msg: String) = {
    val twt = new Tweet(user,new Date)
    if (service.sendTweet(twt)) {
      localCache.saveTweet(twt)
      ui.showTweet(twt)
    }
  }
}

看看实例化时间，这是当DI实际发生(我理解它)，我很难看到蛋糕的优势，特别是当你考虑额外的键盘输入你需要做的蛋糕声明(封闭性状)

//Please note,I have stripped out some implementation details from the 
    //referenced example to clarify the injection of implemented dependencies

    //Cake dependencies injected:
    trait TextClient
        extends TwitterClientComponent
        with TwitterClientUIComponent
        with TwitterLocalCacheComponent
        with TwitterServiceComponent {


      // Dependency from TwitterClientComponent:
      val client = new TwitterClient

      // Dependency from TwitterClientUIComponent:
      val ui = new TwitterClientUI

      // Dependency from TwitterLocalCacheComponent:
      val localCache = new TwitterLocalCache 

      // Dependency from TwitterServiceComponent
      val service = new TwitterService
    }

现在再次与抽象字段，或多或少相同！：

trait TextClient {
          //first of all no need to mixin the components

          // Dependency on TwitterClient:
          val client = new TwitterClient

          // Dependency on TwitterClientUI:
          val ui = new TwitterClientUI

          // Dependency on TwitterLocalCache:
          val localCache = new TwitterLocalCache 

          // Dependency on TwitterService
          val service = new TwitterService
        }

我肯定我必须缺少一些关于蛋糕的优势！但是，目前我看不出它以任何其他方式声明依赖性(构造函数，抽象字段)。