Question

I have a query result of List[ Tuple3[User, Order, OrderItem] ]

To create a case class instance of an Invoice, its companion object takes a User, Order and a List[OrderItem].

Currently I’m hacking it out something like:

def getInvoice(orderNum: String): Option[Invoice] = {

  val res = 
    dao.byOrderNum(orderNum) // List[ Tuple3[User, OrderEntry, OrderItem] ]

  if(!res.isEmpty) {
    val(user, order) = (res(0)._1, res(0)._2)
    val items = res map { case(_, _, oi: OrderItem) => oi }
    Some( Invoices.apply(user, order, items) ) // gets an Invoice
  }
  else None
}

I could make the query result a List[ Option[Tuple3[User, Order, OrderItem]] ], which would let me flatMap over the result, but not sure what that buys me.

At any rate, must be a more concise/elegant solution to the problem

Thanks

Answer 1

The following should be exactly equivalent:

def getInvoice(orderNum: String): Option[Invoice] = {
  val res = dao.byOrderNum(orderNum)

  res.headOption.map {
    case (user, order, _) => Invoices(user, order, res.map(_._3))
  }
}

The key is headOption, which handles the checking for emptiness in a more idiomatic way (it gives None for an empty sequence and Some(xs.head) for a non-empty one).