Using scala.Option functionally - scala

Question

I have an Option, say O, which can either be None or may have some value inside. If it has some value, that value may have a flag, say f. My requirement is that if O is None, then I create an object, say of type MyEntity,but if O has a value with flag as true, I return Nil else I create instance of MyEntity with different value. Java code can be almost as:
if(O.isEmpty) {
MyEntity("x")
} else {
if(O.f) {
Nil
} else {
MyEntity("y") // with different value
}
}
I want to do this in functional style using HoFs provided in scala.Option. What would be best possible way of doing it? I could this so far :
if(O.isEmpty){
MyEntity("x")
} else {
Option.unless(O.exists(_.f))(MyEntity("y"))
}

Answer 1

I misread your question the first go round, so here is attempt #2
This is a great case for pattern matching:
val maybeMyEntity: Option[MyEntity] = option match {
case Some(flagValue) if flagValue => None
// case Some(true) => None (More concise, but does not highlight a handy feature)
case Some(_) => Some(MyEntity("Y"))
case None => Some(MyEntity("X"))
}
Pattern matching is very powerful.
Alternatively, mapping is another option:
mapping of an Option will only occur if its value is not empty, and flatMapping will remove the layer of Option added, from Option[Option[MyEntity]] to Option[MyEntity]
val result: Option[MyEntity] = if (option.isEmpty) {
Some(Entity("X"))
} else {
option.flatMap { flagValue =>
if (flagValue) {
None
} else {
Some(MyEntity("Y"))
}
}
}

Answer 2

As mentioned in the comments, Nil type is a List, and your expression should always return the same type (should really not be Any).
One possibility is to define a "sentinel" value for MyEntity, e.g.:
object MyEntity {
val Nil = MyEntity("")
}
Now you can write:
val result = O.fold(MyEntity("x")) {
case true => MyEntity.Nil
case false => MyEntity("y")
}

Answer 3

case class AnOption(var flag: Boolean = true)
case class MyEntities(name: String)
val myOptionEntityCheck = (someOption: Option[AnOption]) => {
someOption match {
case None => Some(MyEntities("X"))
case Some(aValue: AnOption) if aValue.flag => None
// OR case Some(AnOption(true)) => None
case Some(_) => Some(MyEntities("y"))
}
}