Flags (for Slick 3.0)

flags.scala

import slick.driver.H2Driver.api._

import scala.concurrent.ExecutionContext.Implicits.global

import scala.concurrent.Await
import scala.concurrent.duration._

object EnrichExample extends App {

  sealed case class Flag(val value: Boolean)

  object Flag {
    val True:  Flag = Flag(true)
    val False: Flag = Flag(false)
  }

  implicit val flagMapper = MappedColumnType.base[Flag, Boolean](_.value, Flag.apply)

  case class Message(content: String, important: Option[Flag] = None)

  class MessageTable(tag: Tag) extends Table[Message](tag, "message") {
    def content   = column[String]("content")
    def important = column[Option[Flag]]("important")
    def * = (content, important) <> (Message.tupled, Message.unapply)
  }

  lazy val messages = TableQuery[MessageTable]

  def testData = Seq(
    Message("First!"),
    Message("Party details",      Some(Flag.True)),
    Message("Timesheet reminder", Some(Flag.False))
  )

  import scala.language.higherKinds

  implicit class QueryEnrichment[M,U,C[_]](q: Query[M,U,C]) {
    def notFlagged(selector: M => Rep[Option[Flag]]): Query[M,U,C] =
      q.filter(t => selector(t).isEmpty || selector(t) === Flag.False)
  }

  val prog = for {
    _    <- messages.schema.create
    _    <- messages ++= testData
    msgs <- messages.notFlagged(_.important).result
  } yield msgs

  val db = Database.forConfig("h2chapter01")

  val msgs = db.run(prog).map { _ foreach println }
  Await.result(msgs, 2 seconds)
  db.close
}