is it idiomatic to use `T?` like an optional of type `T`?

# getting-started

[y]

is it idiomatic to use T? like an optional of type T?

[Joffrey]

Yes, though I guess it depends on what you need to express. T? is meant to express "the nullable version of T, no matter whether T is already nullable or not". Note that an unconstrained T is already potentially nullable, depending on the type parameter that's actually passed in a specific usage of your generic declaration

[Kevin Del Castillo]

As Joffrey Bion mention you'd have to constraint your type T to T: Any then you should be able to use T? as an "optional" T

[y]

wait, is this true for a concrete T?

[y]

as in, val foo: Foo? is nullable, but val foo: Foo is not, correct?

[Kevin Del Castillo]

No for concrete types it's not same, the implicit nullability of the type is only true for generics

[y]

okay, phew.

[Joffrey]

Foo is not nullable, Foo? is nullable. Both can be passed as T to a generic declaration if T is not constrained

[y]

oh, yes. that also aligns with my understanding. thanks about that clarification.

so, just making sure: say I’m making a Kotlin class, and I need an optional field (of a non-generic type, let’s say Foo), I should use a Foo?, correct?