Is there a way to ignore a non-matching case?

Question

If I have a match expression, how can I make it automatically ignore a non-match without explicitly doing case _ =>? Is there a way to create a function that does something like this maybe?

Answer 1

You need a generic way to handle "ignoring". Options, among other classes, provide this (among other things). So you can:

val i = 7
Some(i) collect {
  case 3 => "Yay!"
  case 5 => "Boo!"
}

to get None (typed as an Option[String]). So basically, if you change x match to Some(x) collect you get the functionality you want. It is better to do this when one is comfortable with handling options.

Answer 2

Write a generic matcher:

object Match {
    def default: PartialFunction[Any, Unit] = { case _ => }
    def apply[T](x: T)(body: PartialFunction[T, Unit]) = (body orElse default)(x)
}

Example:

scala> 1 to 5 foreach (Match(_) {
     |   case 2 => println("two")
     |   case 3 => println("three")
     | }
     | )
two
three

You might be interested too in PartialFunction's companion object's methods cond and condOpt.