scala - 为什么光滑的投影不起作用

Question

出于某种原因，就我而言，即使是简单的 Slick 表声明也不起作用。我正在使用 slick 2.10 (1.0.0)，这是 maven 中央存储库中的最新版本。

case class DeviceType(id: Option[Int] = None, name: String, version: String)

object DeviceTypes extends Table[DeviceType]("device_types") {

  def id = column[Int]("id", O.PrimaryKey, O.AutoInc)
  def name = column[String]("name", O.NotNull)
  def version = column[String]("version")

  def * = id.? ~ name ~ version <> (DeviceType, DeviceType.unapply _)


  def delete(device_type: DeviceType): Unit = {
database withSession { implicit session : Session =>
  val dt_query = for(dt <- DeviceTypes if dt.id == device_type.id.get) yield dt
    //Query(DeviceTypes).filter(_.id == device_type.id.get)
  dt_query.delete
}
  }
}

[warn] /home/salil/Scala/sd_ventures/app/models/DeviceType.scala:38: scala.slick.lifted.Column[Int] and Int are unrelated: they will most likely never compare equal
[warn]       val dt_query = for(dt <- DeviceTypes if dt.id == device_type.id.get) yield dt
[warn]                            ^

And if I use Query class directly, I get the same warning:
[warn] /home/salil/Scala/sd_ventures/app/models/DeviceType.scala:38: scala.slick.lifted.Column[Int] and Int are unrelated: they will most likely never compare equal
[warn]       val dt = Query(DeviceTypes).filter(_.id == device_type.id.get)
[warn]                                               ^

有人能告诉我为什么它不起作用吗？

Answer 1

在 Slick 中，您必须使用“===”来测试相等性。

val dt_query = for(dt <- DeviceTypes if dt.id === device_type.id.get) yield dt

引用:在 http://slick.typesafe.com/doc/1.0.0/gettingstarted.html 的底部