I have many `enum`s with the following prototype: ...

# getting-started

[Pitel]

I have many `enum`s with the following prototype: enum class SomeHeaders(val label: String) (for headers of different tables). How can I write a type parameter (like val a: ???WHAT???) so that it will be clear that it's enum (so I can use values(), etc.) and it had the label parameter. The parameter has easty solution: interface, but what about the enum limitation?

[Roukanken]

something like this seems to work, with generics:

interface Labeled {
    val label: String
}

enum class LabeledEnum(override val label: String): Labeled {
    THE_ONE("the one")
}

data class LabeledClass(override val label: String): Labeled

fun <T> test(a: T) where T: Enum<T>, T: Labeled {
    println(a)
}

fun main() {
    test(LabeledEnum.THE_ONE)
    test(LabeledClass("not the one")) // this line does not compile
}

without generics it would need so called intersection types, usually written as Enum<T> & Labeled or similarly, sadly Kotlin does not have these, nor there are any plans for them so far

[Roukanken]

for values() you could use enumValues<T>() but that would need to be inside reified inline function

[Pitel]

Tahnk, TIL there is a where keyword exactly for this 👍🏻

[Pitel]

@Roukanken Hmm, but that's still not it. I want to do test(LabeledEnum), like, pass the whole enum, not just single value.

[Pitel]

https://kotlinlang.org/docs/enum-classes.html#working-with-enum-constants ok, this is exactly what I need!