Hi, I’m looking for a way around a compilation error when interacting with specific Java code. I ha...

# getting-started

[mics]

Hi, I’m looking for a way around a compilation error when interacting with specific Java code.

I have a preexisting Java code (in a library, which I cannot change and need to consume) the code like this

class Foo<T extends Enum<T>> {
  Foo(Class<T> type) {}
}

enum FEnum {
  BLAH
}

and then I try to instantiate Foo in Kotlin

fun main(args: Array<String>) {
    val foo = Foo(FEnum::class.java) // works ok, but have to hard-code enum class name here

    val type: Class<out Enum<*>> = FEnum::class.java
    val bar = Foo(type) // Error: doesn't work when class is obtained dynamically 
}

How can I modify the Kotlin code, passing type as some Class, so that Foo constructor accepts it?

[Andreas Sinz]

inline fun <reified T: Enum<T>> createFoo() = Foo(T::class.java)

[Andreas Sinz]

then you are able to create an instance with createFoo<FEnum>()

[mics]

@Andreas Sinz this works, but still requires me to hard code enum name here. But I need to pass it via a variable.

There are many enums in my code, and the enum class name to use is saved in a file, which is later read into a variable of type Class<....> and enum values are iterated via reflection in Foo

[mics]

I cannot pass a variable type to code like createFoo<type>() … it wouldn’t compile

[mics]

basically, if `Foo`s template were written as T extends Enum instead of T extends Enum<T>, then my Kotlin code with Class<out Enum<*>> would work

I don’t understand how I can represent in Kotlin that it’s not just an Enum but Enum of T

[Andreas Sinz]

this is not possible on the JVM because of type erasure

[mics]

so because of type erasure the code would work on Java (with unchecked cast, probably), but cannot be done at all on Kotlin, right?

[Andreas Sinz]

If you can do it in java, you can do it the same way in kotlin