ddd-dip.scala

// base (サンプルなのでただの marker trait)
trait Entity
trait Repository

// domain layer
case class User(id: Int, name: String) extends Entity
trait Users extends Repository {
  def find(id: Int): Option[User]
}

// infra layer
import scalikejdbc._
import SQLInterpolation._

class ScalikeJdbcBasedUsers extends Users {
  private def rsToEntity(rs: WrappedResultSet): User = {
    User(rs.int("id"), rs.string("name"))
  }

  def find(id: Int): Option[User] = {
    DB readOnly { implicit session =>
      sql"select * from users where $id".map(rsToEntity).single().apply()
    }
  }
}