Return second string if first is empty? - scala

Question

Here is an idiom I find myself writing.
def chooseName(nameFinder: NameFinder) = {
if(nameFinder.getReliableName.isEmpty) nameFinder.getReliableName
else nameFinder.secondBestChoice
}
In order to avoid calling getReliableName() twice on nameFinder, I add code that makes my method look less elegant.
def chooseName(nameFinder: NameFinder) = {
val reliableName = nameFinder.getReliableName()
val secondBestChoice = nameFinder.getSecondBestChoice()
if(reliableName.isEmpty) reliableName
else secondBestChoice
}
This feels dirty because I am creating an unnecessary amount of state using the vals for no reason other than to prevent a duplicate method call. Scala has taught me that whenever I feel dirty there is almost always a better way.
Is there a more elegant way to write this?
Here's two Strings, return whichever isn't empty while favoring the first

Answer 1

There's no need to always call getSecondBestChoice, of course. Personally, I find nothing inelegant about the code after changing that - it's clear what it does, has no mutable state. The other answers just seem overcomplicated just to avoid using a val
def chooseName(nameFinder: NameFinder) = {
val reliableName = nameFinder.getReliableName()
if(reliableName.isEmpty) reliableName
else nameFinder.getSecondBestChoice()
}
If you really want to avoid the val, here's another variant (generalises well if there are more than two alternatives)
List(nameFinder.getReliableName(), nameFinder.getSecondBestChoice()).find(_.nonEmpty).get
(or getOrElse(lastResort) if everything in the list may be empty too)

Answer 2

Here's a way using Option. It's not that much prettier, but everything is called only once. This assumes you want a String as a result, and don't care if the second string is empty.
Some(nameFinder.getReliableName)
.filter(_.nonEmpty)
.getOrElse(nameFinder.secondBestChoice)

Answer 3

Option(namefinder.getReliableName) // transforms a potential null into None
.filter(_.trim.nonEmpty) // "" is None, but also " "
.getOrElse(nameFinder.secondBestChoice)
Or better, if you can modify getReliableName to return an Option[String]:
def chooseName(nameFinder: NameFinder): String =
namefinder.getReliableName getOrElse nameFinder.secondBestChoice
Finally, if secondBestChoice can fail as well (assuming it returns an Option[String]):
def chooseName(nameFinder: NameFinder): Option[String] =
namefinder.getReliableName orElse nameFinder.secondBestChoice

Answer 4

If you need it more than once:
scala> implicit class `nonempty or else`(val s: String) extends AnyVal {
| def nonEmptyOrElse(other: => String) = if (s.isEmpty) other else s }
defined class nonempty
scala> "abc" nonEmptyOrElse "def"
res2: String = abc
scala> "" nonEmptyOrElse "def"
res3: String = def

Answer 5

Using the following pattern matching may deliver a neater scalish code,
def chooseName(nameFinder: NameFinder) = {
nameFinder.getReliableName match {
case r if r.isEmpty => r
case _ => nameFinder.secondBestChoice
}
}