Scala Cake Pattern：将大型组件拆分为单独的文件

trait AbstractConfig {
  def config: AbstractConfigInterface
  trait AbstractConfigInterface {
    def test: Unit
  }
}

trait SomeConfig extends AbstractConfig {
  this: Core =>  
  def config = SomeConfigImplementation
  object SomeConfigImplementation extends AbstractConfigInterface {
    def test = println("conf.test method called")
  }
}

trait AbstractDatabase {
  def database: AbstractDatabaseInterface
  trait AbstractDatabaseInterface {
    def connect: Unit
  }
}

trait SomeDatabase extends AbstractDatabase {
  this: Core =>
  def database = SomeDatabaseImplementation
  object SomeDatabaseImplementation extends AbstractDatabaseInterface {
    def connect = {
      println("connect method called")
      core.conf.test
    }
  }
}

trait Core {
  this: AbstractDatabase with AbstractConfig =>
  def core = CoreInterface
  object CoreInterface {
    def db = database
    def conf = config
  }
}

object app extends Core with SomeDatabase with SomeConfig

object Run {
  def main(args: Array[String]) = {
    app.core.db.connect
  }
}

这里的数据库和配置组件(SomeConfig和SomeDatabase特性)是可插拔的,如果需要可以更改为其他一些实现.他们的实现可以访问包含数据库和配置的核心对象,因此数据库可以在需要时访问配置,反之亦然.

所以问题是：如果像SomeDatabase这样的特性变得很大并且不适合单个文件,那么如何将它拆分成单独的类来保留对核心对象的访问？更具体地说,假设我需要将SomeDatabase中的连接方法中的一些代码移动到另一个文件中：

// SomeDatabase.scala
trait SomeDatabase extends AbstractDatabase {
  this: Core =>
  def database = SomeDatabaseImplementation
  object SomeDatabaseImplementation extends AbstractDatabaseInterface {
    def connect = {
      val obj = new SomeClass()
    }
  }
}

// SomeClass.scala in the same package
class SomeClass {
    core.conf.test // Does not compile - how to make it work??
}

SomeClass是SomeDatabase如何工作的实现细节,所以我显然不想把它作为特性并将其混合到应用程序中.有没有办法为SomeClass提供核心对象的访问权限？

一些相关链接：

> Dependency Injection vs Cake Pattern by Jan Machacek
> Real World Scala: Dependency Injection by Jonas Boner
> Dependency Injection in Scala: Extending the Cake Pattern by Adam Warsky
> Scalable Component Abstractions by Martin Odersky & Matthias Zenger