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Lift Mapper 或记录框架中的继承

发布于 2024-09-17 19:38:40 字数 81 浏览 8 评论 0原文

有没有一种方法可以使用 Mapper o Record Framework 在 Lift 中定义正确的继承模型，其中父类有一张表，每个子类有一张表？

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脸赞 2024-09-24 19:38:40

假设您希望使用继承以便能够在每个子类中使用相同的映射字段，我通过使用这些字段的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
}

Assuming you want to use inheritance to be able to use the same mapped fields in each of the subclasses, I've approached this by using a trait for those fields:

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

Then each Mapper/MetaMapper will extend SuperFields, but define their own database table and connection identifiers:

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
}

And:

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
}

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