Question

我试图使用一个简单的自定义光滑列示例as described in here。鉴于此＆＃34; enum＆＃34;：

trait EntityType

object EntityTypeImplicits {
  implicit def fromString(s: String): EntityType = s match {
    case "external" => ExternalEntity()
    case "user" => UserEntity()
    case "packet" => PacketEntity()
    case "share" => ShareEntity()
    case _ => throw new RuntimeException("Unknown entity type")
  }
  implicit def toString(e: EntityType): String = e match {
    case ExternalEntity() => "external"
    case UserEntity()     => "user"
    case PacketEntity()   => "packet"
    case ShareEntity()    => "share"
  }
}

case class ExternalEntity() extends EntityType
case class UserEntity() extends EntityType
case class PacketEntity() extends EntityType
case class ShareEntity() extends EntityType

case class Entity(identity: String, entityType: EntityType)

和此架构配置

trait Schema extends HasDatabaseConfigProvider[JdbcProfile] {
  import driver.api._

  implicit val entityTypeMapper =
    MappedColumnType.base[EntityType, String] _
  implicit val tt: TypedType[EntityType]

  class Entities(tag: Tag) extends Table[Entity](tag, "entities") {
    def identity = column[String]("identity", O.PrimaryKey)
    def entityType = column[EntityType]("type")
    def * = (identity, entityType) <>
            (Entity.tupled, Entity.unapply)
  }
}

这会产生编译错误：

[error] No matching Shape found.
[error] Slick does not know how to map the given types.
[error] Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List).
[error]   Required level: slick.lifted.FlatShapeLevel
[error]      Source type: (slick.lifted.Rep[String], slick.lifted.Rep[domain.EntityType])
[error]    Unpacked type: (String, domain.EntityType)
[error]      Packed type: Any
[error]     def * = (identity, entityType) <>
[error]                                    ^

我不明白 - 我已经提供了映射规则，因此Slick实际上可以转换我的＆＃34; enum＆＃34;为了串起来，为什么他会抱怨？

P.S。我是非常 Slick的新手（和Scala一样，老实说）。

Answer 1

按照the docs中的示例，它基本上看起来没有正确设置映射对象。

 implicit val entityTypeMapper = MappedColumnType.base[EntityType, String] (
      EntityTypeImplicits.toString,
      EntityTypeImplicits.fromString)

这应该可以解决这个问题......你基本上需要给两个能够执行这种转换的功能（通过给出下划线，不确定你在做什么？）。我在表类中也有更明确定义的类型信息，但我怀疑这很重要，只是为了帮助排除故障...

def entityType : Rep[EntityType] = column[EntityType]("type")

希望有所帮助！我发现Slick文档有点meh，＆amp;谷歌搜索可以引导你进入一个被弃用的语法兔子洞......

Scala Slick 3.1简单列＆lt; - ＆gt;案例类映射器

1 个答案: