typeclass.scala

object TypeSerializers { 
  implicit object LongPropertySerializer extends PropertySerializer[Long] {
    def sqlType = "long"
  }

  implicit object StringPropertySerializer extends PropertySerializer[String] {
    def sqlType = "string"
  }
}

trait TaskProperties {
  import TypeSerializers._
  var id: Property[Long]              = Property("id", None)
  var title: Property[String]         = Property("title", None)
  val properties = List(id, title)

  def toSQL() = {
    properties.map((p: Property[_]) =>
      p.name + " " + Property.sqlType(p)).mkString(", ") + ", FOREIGN KEY(task_list_id) REFERENCES task_list(id)"
  }
}

object Property {
  def apply[T](name: String, value: Option[T]) = new Property(name, value)

  def sqlType[T](p: Property[T])(implicit propertySerializer: PropertySerializer[T]): String =
    propertySerializer.sqlType

}

class Property[T](val name: String, var value: Option[T])


[error] Task.scala:28: could not find implicit value for parameter propertySerializer: com.android.todoapp.PropertySerializer[_$1]
[error]       p.name + " " + Property.sqlType(p)).mkString(", ") + ", FOREIGN KEY(task_list_id) REFERENCES task_list(id)"