Question

sometimes I write code like the following:

val item1 = list.find(_.source.name.equals("foo"))
if (item1.isDefined) doSomething1(item1)
else {
  val item2 = list.find(_.dest.name.equals("bar"))
  if (item2.isDefined) doSomething2(item2)
  else doSomethingElse()
}

Does anyone have a nicer Scala syntax for laying this code out?

Answer 1

I’d write this as

list.find(_.source.name =="foo").fold(doSomething1) {
  list.find(_.dest.name == "bar").fold(doSomething2)(doSomethingElse)
}

but that is because I have added the method fold to Option like so:

class FoldableOption[A](o: Option[A]) {
  def fold[Z](f: A => Z)(g: => Z) = o.map(f).getOrElse(g)
}
implicit def option_has_folds[A](o: Option[A]) = new FoldableOption(o)

If you don’t want to add the fold method, you can also use the map, getOrElse pair:

list.find(_.source.name == "foo").map(doSomething1).getOrElse {
  list.find(_.dest.name == "bar").map(doSomething2).getOrElse(doSomethingElse)
}

which is not much more verbose.