Anyone know if its possible to have a generic func...

# getting-started

[Siddhartha Juluru]

Anyone know if its possible to have a generic function accept both a non-null and nullable enum? I current have an func. built like this

fun <P : Enum<P>> BaseConstraints<out Any, P>.validEnum(
    init: Unit.() -> Unit
) {
    this.rules.add(ValidEnum())
}

and it is only valid when I do validEnum<Status> { } (where Status is my enum) but not when I do validEnum<Status?> { } . I can make it accept the latter by doing

fun <P : Enum<P>> BaseConstraints<out Any, P?>.validEnum(
    init: Unit.() -> Unit
) {
    this.rules.add(ValidEnum())
}

but then I am unable to do validEnum<Status> { }

[Siddhartha Juluru]

Figured out I can do this instead

@JvmName("validEnumAnyP")
fun <P: Enum<P>> BaseConstraints<out Any, P>.validEnum(
    init: Unit.() -> Unit
) = this.rules.add(ValidEnum())

@JvmName("validEnumAnyP?")
fun <P: Enum<P>> BaseConstraints<out Any, P?>.validEnum(
    init: Unit.() -> Unit
) = this.rules.add(ValidEnum())

[Youssef Shoaib [MOD]]

You could have fun <P: Enum<P & Any>?> I think, since then both Status and Status? extend Enum<Status>?

[Siddhartha Juluru]

Thanks, that seems to work! If I am reading this correctly, doing P & Any is as if doing P: Any

[Youssef Shoaib [MOD]]

Sort of, what it is really doing is that, AFAIK, Enum<T> requires T : Enum<T>, and NOT T : Enum<T>?, But we would like to make our P here nullable within the type parameters, and so we simply make it possibly nullable, but we ensure to only pass the non-nullable kind to Enum so that it compiles correctly.

[Siddhartha Juluru]

I see, thanks!