is it possible to have a custom property delegate ...

# announcements

[parth]

is it possible to have a custom property delegate that can provide a nullable value to a nullable property and a non-nullable value to a non-nullable field? aka:

class Foo {
    val one : String by someProperty()
    val two : String? by someProperty()
}

….and if so, what would be the signature of operator fun getValue(…)?
I guess I could do val two : String? by someOptionalProperty() to make the type signature easier, but that feels like I’m giving up, y’know?

[bezrukov]

it's possible (a bunch of delegates from stdlib allows this, e.g. lazy)
just leave it as T and perform unchecked cast if necessary (like return null as T)

[parth]

🤦🏾‍♂️ that makes perfect sense, thank you!

[araqnid]

there’s also the option of using provideDelegate if you want to return different implementations for nullable vs non-nullable properties (Gradle’s kotlin-dsl does this for project properties, for example)