How do I pass a value of a non-null type to a met...

# announcements

[Ben Piatt]

How do I pass a value of a non-null type to a method that accepts that type but as a nullable parameter? The other way around makes sense to safe-check, but if I'm giving you a non-nullable type as a parameter and you can accept nullable types, there's gotta be a way it can be taken

[Shawn]

This should just work normally - you can definitely pass, for example String to a function that takes String?

[Shawn]

you should also be able to pass a non-null generic type to a function that takes a nullable one

[Shawn]

Unless you mean you’re trying to pass a Column<Int> to a function that takes Column<Int?>

[Ben Piatt]

The latter

[Ben Piatt]

Sorry, not quite, Column<Int>?

[Shawn]

If that’s the case, you should just be able to use it intuitively

[Ben Piatt]

Actually so my full type is Column<EntityID<Int>?>

[Shawn]

oh

[Ben Piatt]

So the nullable part is the EntityID inside of the Column, that's what it doesn't like

[karelpeeters]

Then you need to look at variance: https://kotlinlang.org/docs/reference/generics.html#variance

[Ben Piatt]

Ok thanks I'll take a look

[karelpeeters]

Foo<X> is not necessarily a subtype of Foo<X?>, it can be the other way around or not at all.

[Ben Piatt]

Gotcha, ok yeah that kinda sucks because I have some helper methods that encapsulate common logic and I basically have to create a copy of the same method with a different name and it does the exact same thing just because of the type issue

[Shawn]

you might be able to do what you want with the correct type projections, though

[Ben Piatt]

I'll definitely try

[karelpeeters]

Yeah it doesn't "suck", it's the typesystem forcing you to make your code more correct!

[Ben Piatt]

Agreed haha I definitely like it better than the alternative