CODEWITHSUNDEEP
scalascala-2.8
Kevin
Kevin

Reputation: 25269

scala returning tuples from functions

Lets say I have something like this:

def f () = {

   var v = someLookupToV()

   match v {
       case Some(v) => (v.id, someOtherLookup(v.id))
       case None => None // <<-- doesn't work, but I'm not sure what to put there!
   }

}

Sort of assuming that someLookupToV returns some object, that has a field id, and then I have some other lookup based on v.id. I want to return both values as a tuple. But what do I do if Some(v) doesn't match anything? What do I return? None and (None,None) didnt' work. Scala accepted (null,null) but I've got no clue if that's the right thing to do...

Upvotes: 2

Views: 1818

Answers (2)

Madoc
Madoc

Reputation: 5919

I would not have the function return (Int, Option[Int]), but instead Option[(Int, Option[Int])]:

def f = someLookupToV match {
  case Some(v) => Some(v.id, someOtherLookup(v.id))
  case None => None
}

or, somewhat shorter:

def f = someLookupToV.map(v => (v.id, someOtherLookup(v.id)))

Upvotes: 15

Gigatron
Gigatron

Reputation: 2055

If you want to return (None, None), your "case Some" line needs to return a tuple of (Option, Option).

As written in your example, your case Some is returning (Int, Option). That's assuming your v.id is an Int and someOtherLookup returns an Option.

Upvotes: 1

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