Question

As a Java-to-Scala switcher, I routinely find myself rewriting null handling stuff like

val itemOpt: Option[Item] = items.get(coords) // "items" is something like a Map
if (itemOpt.isDefined) {
  val item = itemOpt.get
  // do something with item, querying item fields a lot of times, for example
  if (item.qty > 10) {
    storeInVault(item.name, item.qty, coords)
  } else {
    storeInRoom(item)
  }
}

I guess it looks ugly and it really looks like a piece of code rewritten from Java’s:

Item item = items.get(coords);
if (item != null) {
  // do something with item, querying item fields a lot of times, for example
}

It also looks ugly in Java, but at least it’s one line less. What is the best practice to handle such simple cases in Scala? I already know of flatMap and flatten to handle collections of Option[Stuff], and I know of getOrElse to handle default values. I dream of something like:

items.get(coords).doIfDefined(item =>
  // do stuff with item
)

but I don’t see anything like that in Option API.

Answer 1

Very popular usage pattern:

val item: Option[Int] = None
val result = item map (_ + 1) getOrElse 0

so you just use map in order to transform value if it’s defined.

If you just want to use value, that is stored within an Option, then just use foreach:

item foreach { it =>
    println(it)
}

As you can see, Option also supports many collection methods, so you actually don’t need to learn new API. You can just treat it as a collection with either 1 or 0 elements.