Scala: join iterators with values in a wrapper

Question

I have the following types: A, B and C, so B <: A and C <: A

I need to get the Iterator[A] that works like this:

• If the current value is of type B, then return B

• If the current value is of type C, then invoke function parse(c: C) : Iterator[B] and then use this iterator until it exhausts. Then continue with the value from the "parent" iterator.

What is the best way to do so in Scala?

Answer 1

Use pattern matching and flatMap:

val itA: Iterator[A] = // ...
val itB: Iterator[B] = itA.flatMap(a => a match {
  case b: B => Iterator(b)
  case c: C => parse(c)
})