我有一个这样的伴生对象：
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
}
}
案例类Address。
因为我有很多这样的对象（每个都定义一个表），所以我想findAll在一个 trait 中移动方法，使其具有通用性，我试图这样做：
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
}
}
}
如您所见，entities它基本上是我的伴侣对象。
现在的问题是我不能像这样重写我的对象定义：
object Addresses extends Table[Address]("address") with DbGenericOperations[Address, Addresses]{
因为它说那Addresses不是一种类型......
我对 scala 很陌生，我想知道：有没有办法解决这个问题？
更新：我已经这样做了：
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：
object Addresses extends Table[Address]("address") with DbGenericOperations[Address]
但我不喜欢使用这种方法：
val results = Addresses.findAll(limit, offset, Addresses)
请让我知道是否有更好的解决方案...