Library support for Scala's NotNull trait

Question

Notice: As of Scala 2.11, NotNull is deprecated.

As far as I understand, if you want a reference type to be non-nullable you have to mixin

Answer 1

I don't really know what the deal is with NotNull, but I get the impression that Scala hasn't fully worked out how it wants to deal with NotNull/Nullable concepts. My own policy is to never use null in Scala, and if you call a Java API that may return null, immediately convert it to an Option.

This utility method is my best friend:

def ?[A <: AnyRef](nullable: A): Option[A] = if (nullable eq null) None else Some(nullable)

Then you do stuff like this:

val foo: Option[Foo] = ?(getFooFromJavaAPIThatMightReturnNull())

I find this far simplier than trying to track what may or may not be null.

So I didn't answer your question at all, but I pass this on in case it's useful...

Update: more recent Scala versions now support this in the standard API:

val foo: Option[Foo] = Option(getFooFromJavaAPIThatMightReturnNull())