Scala: convert string to Int or None - scala

Question

I am trying to get a number out of an xml field
...
<Quantity>12</Quantity>
...
via
Some((recipe \ "Main" \ "Quantity").text.toInt)
Sometimes there may not be a value in the xml, though. The text will be "" and this throws an java.lang.NumberFormatException.
What is a clean way to get either an Int or a None?

Answer 1

scala> import scala.util.Try
import scala.util.Try
scala> def tryToInt( s: String ) = Try(s.toInt).toOption
tryToInt: (s: String)Option[Int]
scala> tryToInt("123")
res0: Option[Int] = Some(123)
scala> tryToInt("")
res1: Option[Int] = None

Answer 2

Scala 2.13 introduced String::toIntOption:
"5".toIntOption // Option[Int] = Some(5)
"abc".toIntOption // Option[Int] = None
"abc".toIntOption.getOrElse(-1) // Int = -1

Answer 3

More of a side note on usage following accepted answer. After import scala.util.Try, consider
implicit class RichOptionConvert(val s: String) extends AnyVal {
def toOptInt() = Try (s.toInt) toOption
}
or similarly but in a bit more elaborated form that addresses only the relevant exception in converting onto integral values, after import java.lang.NumberFormatException,
implicit class RichOptionConvert(val s: String) extends AnyVal {
def toOptInt() =
try {
Some(s.toInt)
} catch {
case e: NumberFormatException => None
}
}
Thus,
"123".toOptInt
res: Option[Int] = Some(123)
Array(4,5,6).mkString.toOptInt
res: Option[Int] = Some(456)
"nan".toInt
res: Option[Int] = None

Answer 4

Here's another way of doing this that doesn't require writing your own function and which can also be used to lift to Either.
scala> import util.control.Exception._
import util.control.Exception._
scala> allCatch.opt { "42".toInt }
res0: Option[Int] = Some(42)
scala> allCatch.opt { "answer".toInt }
res1: Option[Int] = None
scala> allCatch.either { "42".toInt }
res3: scala.util.Either[Throwable,Int] = Right(42)
(A nice blog post on the subject.)