Is there a predefined function x in Scala that combine 2 Options so that
Some(a) x None => Some(a)
None x Some(b) => Some(b)
None x None => None
Yes, this is the orElse
method. It chooses the first defined value, or None
if neither is defined.
scala> Some(1) orElse None
res0: Option[Int] = Some(1)
scala> None orElse Some(1)
res1: Option[Int] = Some(1)
scala> None orElse None
res2: Option[Nothing] = None
scala> Some(1) orElse Some(2)
res3: Option[Int] = Some(1)
It's not hard to do it by hand:
scala> val a = Some(1)
a: Some[Int] = Some(1)
scala> val b = Some(2)
b: Some[Int] = Some(2)
scala> Seq(a,b).flatten.headOption
res0: Option[Int] = Some(1)
In the question comments, you mention you can't have Some(a)
and Some(b)
, so what you really have is Option[Either[Int,Int]]
. In that case, you can use x.map(_.merge)
to get back to Option[Int]
, eg
scala> val x:Option[Either[Int,Int]] = Some(Left(2))
x: Option[Either[Int,Int]] = Some(Left(2))
scala> x.map(_.merge)
res0: Option[Int] = Some(2)
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