Kotlin define interface for enum class values method

Question

if I define an enum class, let's say:

enum class MyEnum { }

I can do the following as enum class all have a values method:

val values = MyEnum.values()

Now I want my enum to implement an interface and have access to the values() method:

enum class MyEnum : EnumInterface { }

interface EnumInterface {
    fun values() : Array<T>

    fun doStuff() {
        this.values()
    }

}

This doesn't compile and I'm sure how to type the values method. Is it possible to define such interface? Thanks!

asm0dey · Accepted Answer · 2019-05-14 10:05:38Z

7

You were really close to correct answer. You need to define generic interface and you enum should extend it typed with enum's class like this:

enum class MyEnum : EnumInterface<MyEnum> {
    A,B,C;
    override fun valuesInternal() = MyEnum.values()
}

interface EnumInterface<T> {    
    fun valuesInternal():Array<T>

    fun doStuff() {
        this.valuesInternal()
    }
}

edited May 14, 2019 at 10:05

answered May 14, 2019 at 9:35

asm0dey

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3 Comments

lorenzo Over a year ago

Thanks for replying! It does compile when MyEnum is empty, but unfortunately does not when adding cases

lorenzo Over a year ago

I would have loved to avoid the valuesInternal() implementation but it does the job, thanks! :)

asm0dey Over a year ago

@lorenzo to a pity you can't make values to be override method and that's why it won't work.

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