Question

I have a code segment something like this:

def test() : Seq[Int] = 
  List("A", "B", "C") collect {
    case "A" => 1
    case "B" => 2
    //case _ => println(_)
  }

Now I would like to print specific values (just for debugging) on the output without adding any elements to the resulting collection. If I uncomment the commented line, Scala infers the value of the expression to Seq[Any], which is completely understandable.

Anybody got any hints how to do this? Thanks in advance!

Answer 1

flatMap

List("A", "B", "C") flatMap {
    case "A" => List(1)
    case "B" => List(2)
    case x => println(x); Nil
}

collect/flatten

List("A", "B", "C").collect {
    case "A" => Some(1)
    case "B" => Some(2)
    case x => println(x); None
}.flatten