use None or EmptyMyObj in scala? [closed]

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I understand the concept of None I also understand how nice it is to have MyObj and also MyEmptyObj but i cant figure out when its better to use None instead of MyEmptyObj and when I should be using MyEmptyObj instead of None. Also I tend not to like to see methods that return Option[MyObj] it clutters my code I prefer to return MyObj and then seamlessly call its methods such as MyObj.toJson and thus MyEmptyObj.toJson will know to represent itself rather than having case None: return some empty json what do you think about this whole subject? To the other side I can say that None goes very well with flatMap etc, so which to choose?

when to None

and when to Empty?

Answer 1

None is great when you have no default value, but if you have a default, by all means use it.

As a very simple example, if you wanted to define a function called amountOwed, you could do this:

def amountOwed(bill: Int, alreadyPaid: Option[Int]): Option[Int] = {
  val owed = bill - alreadyPaid.getOrElse(0)
  if(owed == 0) None // nothing to pay!
  else Some(owed)
}

But that's much more complex (and annoying) than it needs to be, since 0 makes perfect sense as both a "haven't paid anything" and "don't owe anything":

def amountOwed(bill: Int, alreadyPaid: Int): Int = {
  bill - alreadyPaid
}