提升映射器或记录框架中的继承

Question

有没有办法使用 Mapper o Record Framework 在 Lift 中定义正确的继承模型，其中父类有一个表，每个儿子有一个表？

Answer 1

假设您希望使用继承能够在每个子类中使用相同的映射字段，我已经通过对这些字段使用特征来解决这个问题:

trait SuperFields[T <: Mapper[T]] {
  self: T =>
  object DESCRIPTION extends MappedString[T](this, 255)
  object BRAND extends MappedString[T](this, 50)
  // etc
}

然后每个 Mapper/MetaMapper 将扩展 SuperFields，但定义自己的数据库表和连接标识符:

class Product extends Mapper[Product] with SuperFields[Product] {
  override def getSingleton = Product
}

object Product extends Product with MetaMapper[Product] {
  override def dbTableName = "PRODUCT"
  override def dbDefaultConnectionIdentifier = SomeConnection
}

和:

class Service extends Mapper[Service] with SuperFields[Service] {
  override def getSingleton = Service
}

object Service extends Service with MetaMapper[Service] {
  override def dbTableName = "SERVICE"
  override def dbDefaultConnectionIdentifier = SomeOtherConnection
}