mutable.PriorityQueue custom ordering for a class with more attributes

Question

So I have something like:

class MyClass(val flag: Boolean, val value1: Double, val value2: Double)

And I would like to have a mutable PriorityQueue where objects of type MyClass are ordered according to a custom order, e.g.:

// I will only ever compare things with the same flag
def compare(this: MyClass, that: MyClass) = {
    val temp = this.value1 compare that.value1
    if(this.flag) temp = -temp // reversing the order of value1
    if(temp != 0) temp else this.value2 compare that.value2
}

In words, each object has a flag and depending on that I'd like to order based on value1. If value1 is equal in both objects, then I only care about value2.

And then I'd like to have something like

val queue = new PriorityQueue[MyClass](...?

Thank you :)

---

Test case 1:

  val queue = mutable.PriorityQueue[Order]()(Ordering.by{ord => (ord.price, ord.timestamp)})

  val o1 = new Order(13, 3, idleStatus)
  val o2 = new Order(11, 1, idleStatus)
  val o3 = new Order(12, 2, idleStatus)
  val o4 = new Order(15, 5, idleStatus)
  val o5 = new Order(14, 4, idleStatus)

  println(queue)
  queue.enqueue(o1)
  queue.enqueue(o2)
  queue.enqueue(o3)
  queue.enqueue(o4)
  queue.enqueue(o5)
  println(queue)

Prints the following:

PriorityQueue()
PriorityQueue((15, 5), (14, 4), (12, 2), (11, 1), (13, 3))

Which is wrong

Answer 1

It looks like maybe this is all you need.

val queue = mutable.PriorityQueue[MyClass]()(Ordering.by{mc =>
  if (mc.flag) (-mc.value1,mc.value2) else (mc.value1,mc.value2)
})