Converting empty string to a None in Scala

Question

I have a requirement to concatenate two potentially empty address lines into one (with a space in between the two lines), but I need it to return a None if both address lines are None (this field is going into an Option[String] variable). The following command gets me what I want in terms of the concatenation:

Seq(myobj.address1, myobj.address2).flatten.mkString(" ")

But that gives me an empty string instead of a None in case address1 and address2 are both None.

Answer 1

This converts a single string to Option, converting it to None if it's either null or an empty-trimmed string:

(kudos to @Miroslav Machura for this simpler version)

Option(x).filter(_.trim.nonEmpty)

Alternative version, using collect:

Option(x).collect { case x if x.trim.nonEmpty => x }

Answer 2

Assuming:

val list1 = List(Some("aaaa"), Some("bbbb"))
val list2 = List(None, None)

Using plain Scala:

scala> Option(list1).map(_.flatten).filter(_.nonEmpty).map(_.mkString(" "))
res38: Option[String] = Some(aaaa bbbb)

scala> Option(list2).map(_.flatten).filter(_.nonEmpty).map(_.mkString(" "))
res39: Option[String] = None

Or using scalaz:

import scalaz._; import Scalaz._
scala> list1.flatten.toNel.map(_.toList.mkString(" "))
res35: Option[String] = Some(aaaa bbbb)

scala> list2.flatten.toNel.map(_.toList.mkString(" "))
res36: Option[String] = None