Question

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Scala: short form of pattern matching that returns Boolean

In my scala code I’m finding myself often writing things like the following:

x match{
   case Type(params) => doStuffWith(params)
   case _ => /* do nothing*/
}

Is there already some predefined operator to do this? I think it would be much clearer if I could write things like:

if( x match Type(params)) {
    doStuffWith(params)
}

essentially avoiding the weird otherwise case. I’ve also had other situations where being able to verify if something matches a pattern in an inline fashion would save me an extra pair of braces.

I know this sort of thing might only be more useful when writing more iterative code, but Scala seems to have so many hidden features I was wondering whether someone has a simple solution for this.

Answer 1

You could lifta partial function from Any to A into a function from Any to Option[A].

To make the syntax nice first define an helper function:

def lifted[A]( pf: PartialFunction[Any,A] ) = pf.lift

Then, make profit:

val f = lifted {
  case Type(i) => doStuff(i)
}

scala> f(2)
res15: Option[Int] = None

scala> f(Type(4))
res16: Option[Int] = Some(8)

The doStuff method will be called only if the argument matches. And you can have several case clauses.