Scala: Boolean to Option

Question

I have a Boolean and would like to avoid this pattern:

if (myBool) 
  Option(someResult) 
else 
  None

What I\'d like to do is

Answer 1

Scalaz has a way to do it with BooleanOps.option. That would allow you to write :

myBool.option(someResult)

If you don't want to add a Scalaz dependency, just add the following in your code :

implicit class RichBoolean(val b: Boolean) extends AnyVal {
  final def option[A](a: => A): Option[A] = if (b) Some(a) else None
}

Answer 2

class RichBool[T](a: Boolean, res:=> T) {
   def toOption: Option[T] = if (a) Some(res) else None
}
implicit def boolToRichBool[T](tp: (Boolean, T)): RichBool[T] = new RichBool(tp._1, tp._2);

This would give you:

(true, 5).toOption // Some(5);
(false, 3).toOption // None

Answer 3

Here are a couple things I would consider:

val bool: Boolean = ???
val result = 1337    

Option(bool).withFilter(identity).map(_ => result)

or

for {
  opt <- Option(bool)
  if opt
} yield result

Answer 4

Another choice:

implicit class RichOptionCompanion(val self: Option.type) extends AnyVal {
  def when[A](cond: Boolean)(value: => A): Option[A] = if(cond) Some(value) else None
}

Usage:

Option.when(foo != "bar") { ... }

Answer 5

Starting Scala 2.13, Option has a when builder for this exact purpose:

Option.when(condition)(result)

For instance:

Option.when(true)(3)
// Option[Int] = Some(3)
Option.when(false)(3)
// Option[Int] = None

Also note Option.unless which promotes the opposite condition.

Answer 6

scala> PartialFunction.condOpt(5) { case x if true => x }
res9: Option[Int] = Some(5)

scala> PartialFunction.condOpt(5) { case x if false => x }
res10: Option[Int] = None

Here, the guard holds the condition and the value passed to condOpt is the value returned if the guard evaluates to true.