Why can I not call .values() on generic enum class?

Question

I know that calling .values() on an enum class gives an array of the enum cases. However it doesn't work with a generic enum class. Why is this, and what can I do to get the same functionality?

class EnumEditActivity<E: Enum<E>>() {    
    var value: E? = null
    var allValues: Array<E> = E.values()
}

If I call values() on a normal enum, it works fine:

enum class Gender {
    male, female
}

for (value in Gender.values()) {
    println(value.name)
}

prints:

male
female

Some answers suggest doing something like this:

enum class SomeEnum {
    one, two
}

class EnumEditActivity<E: SomeEnum>() {    
    var value: E? = null
    val values = listCases<SomeEnum>()

    inline fun <reified E: SomeEnum> listCases() = (E::class.java).enumConstants.toList()
}

This doesn't work because it's not dynamic: it will always just get the cases for SomeEnum, so there's no point having a generic class. You can't pass any other enum apart from SomeEnum into the class, because one enum cannot inherit from another.

I don't think this is possible in Kotlin. I'm now just defining the class so it requires you to pass in an array of the enum's cases in the class initializer:

class EnumEditActivity<E>(val values: Array<E>)

Answer 1

Because you have to call the function into the instance, not the type, to do so you have to reify the type variable:

interface  VisualEnum {
    fun get(fromName : String)
}

enum class VisuelEnumSub(lowerName: String) : VisualEnum {
    A("a"), B("b"), C("c");

    override fun get(name : String) {
        VisuelEnumSub.values().filter { it.toString().equals(name, true) }
    }}

open class AppCompatActivity{}

open class EnumEditActivity<E: VisualEnum>(): AppCompatActivity() {
    inline fun <reified A:E> onCreate() = (A::class.java).enumConstants
}

fun main(args: Array<String>) {
   EnumEditActivity<VisuelEnumSub>().onCreate<VisuelEnumSub>().forEach { println(it) }
}

result:

A
B
C

Answer 2

You can only do this by passing the class as a parameter (because E is a class type parameter and reified isn't available):

class EnumEditActivity<E: Enum<E>>(cls: Class<E>) {    
    var value: E? = null
    var allValues: Array<E> = cls.enumConstants
}

inline fun <reified E: Enum<E>> EnumEditActivity() = EnumEditActivity(E::class.java)

// call as
EnumEditActivity<YourEnum>()

Or with your

class EnumEditActivity<E>(val values: Array<E>)

you can use the standard enumValues function:

inline fun <reified E: Enum<E>> EnumEditActivity() = EnumEditActivity(enumValues<E>())