Scala泛型问题

我有一个这样的伴星：

object Addresses extends Table[Address]("address"){
  //some mapping columns
  .... 

  //a method I want to made generic 
  def findAll(limit: Option[Int], offset: Option[Int]): Seq[Address] = DBTest.db.withSession { implicit db: Session =>
    (limit, offset) match {
      case (Some(l), Some(o)) => Addresses.map { a => a }.drop(o).take(l).list
      case (None, None) => Addresses.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
      case (Some(l), None) => Addresses.map { a => a }.take(l).list
      case (None, Some(o)) => Addresses.map { a => a }.drop(o).list
    }
  }

trait DbGenericOperations[T, U <: Table[T]]{
  val entities: U
  /**
   * Based on REST conventions, for listing it's good to use limit and offset, like: /entities?limit=25&offset=50.
   */
  def findAll(limit: Option[Int], offset: Option[Int]): Seq[T] = DBTest.db.withSession { implicit db: Session =>
    (limit, offset) match {
      case (Some(l), Some(o)) => entities.map { a => a }.drop(o).take(l).list
      case (None, None) => entities.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
      case (Some(l), None) => entities.map { a => a }.take(l).list
      case (None, Some(o)) => entities.map { a => a }.drop(o).list
    }
  }
}

trait DbGenericOperations[T]{
      /**
       * Based on REST conventions, for listing it's good to use limit and offset, like: /entities?limit=25&offset=50.
       */
      def findAll(limit: Option[Int], offset: Option[Int], entities: Table[T]): Seq[T] = DBTest.db.withSession { implicit db: Session =>
        (limit, offset) match {
          case (Some(l), Some(o)) => entities.map { a => a }.drop(o).take(l).list
          case (None, None) => entities.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
          case (Some(l), None) => entities.map { a => a }.take(l).list
          case (None, Some(o)) => entities.map { a => a }.drop(o).list
        }
      }
    }

案例类别的

地址

因为我有很多这样的对象（每个对象定义一个表），所以我想将

findAll

方法移动到一个特性中，使其成为通用的，我尝试这样做：

object Addresses extends Table[Address]("address"){
  //some mapping columns
  .... 

  //a method I want to made generic 
  def findAll(limit: Option[Int], offset: Option[Int]): Seq[Address] = DBTest.db.withSession { implicit db: Session =>
    (limit, offset) match {
      case (Some(l), Some(o)) => Addresses.map { a => a }.drop(o).take(l).list
      case (None, None) => Addresses.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
      case (Some(l), None) => Addresses.map { a => a }.take(l).list
      case (None, Some(o)) => Addresses.map { a => a }.drop(o).list
    }
  }

trait DbGenericOperations[T, U <: Table[T]]{
  val entities: U
  /**
   * Based on REST conventions, for listing it's good to use limit and offset, like: /entities?limit=25&offset=50.
   */
  def findAll(limit: Option[Int], offset: Option[Int]): Seq[T] = DBTest.db.withSession { implicit db: Session =>
    (limit, offset) match {
      case (Some(l), Some(o)) => entities.map { a => a }.drop(o).take(l).list
      case (None, None) => entities.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
      case (Some(l), None) => entities.map { a => a }.take(l).list
      case (None, Some(o)) => entities.map { a => a }.drop(o).list
    }
  }
}

trait DbGenericOperations[T]{
      /**
       * Based on REST conventions, for listing it's good to use limit and offset, like: /entities?limit=25&offset=50.
       */
      def findAll(limit: Option[Int], offset: Option[Int], entities: Table[T]): Seq[T] = DBTest.db.withSession { implicit db: Session =>
        (limit, offset) match {
          case (Some(l), Some(o)) => entities.map { a => a }.drop(o).take(l).list
          case (None, None) => entities.map { a => a }.drop(ConfigurationsLoader.DefaultOffset).take(ConfigurationsLoader.DefaultLimit).list
          case (Some(l), None) => entities.map { a => a }.take(l).list
          case (None, Some(o)) => entities.map { a => a }.drop(o).list
        }
      }
    }

并像这样声明伴随对象：

对象地址使用DbGenericOperations[Address]扩展表[Address]（“Address”）

但我不喜欢使用这种方法：

val结果=地址。findAll（限制、偏移、地址）

---

请告诉我是否有更好的解决方案…

为什么不创建一个类/特征RichTable[T]（…）extends Table[T]（…）来添加此方法？

因为当我必须扩展Table[T]时，我还必须指定表名：

extends Table[Address]（“Address”）

所以我不再使用泛型案例…不明白。抽象类RichTable[T]（名称：String）扩展表[T]（名称）{…}