```interface Criteria<T: Criteria<T>> ...

# getting-started

[jeggy]

interface Criteria<T: Criteria<T>> { fun test(): T }

open class Filter1(val data: String = ""): Criteria<Filter1> {
    override fun test() = Filter1("Basic")
}

object Standard: Filter1() {}

// How can I provide some correct type here?
fun whatever(): Criteria<*> {
    // Some custom code...
    return Standard
}

fun main() {
    println(whatever().data) 
}

Could someone help me with my whatever function here, so it returns the correct type? (playground: https://pl.kotl.in/z4lPq_kWE)

[Adam Cooper]

It looks like you have a recursive interface declaration.

interface Criteria<T: Criteria<T>>

Is that intentional?

[jeggy]

Yes

[Adam Cooper]

How does that work? It seems infinitely recursive.

[jeggy]

Just makes it possible to give a generic type of itself to a interface. Just like shown with the Filter1 type.

[Youssef Shoaib [MOD]]

This works:

fun whatever(): Criteria<Filter1>

However, you still won't be able to do .data though. That's because a Criteria<Filter1> is not guaranteed to be of type Filter1
You could instead just do:

fun whatever(): Filter1

[jeggy]

My actual code has multiple implementations of Criteria . So it's important that it's not only supporting the Filter1 .

[Youssef Shoaib [MOD]]

Well, how is whatever meant to decide what its return type is though? As in, you can't access .data on an arbitrary Criteria<*>. Is whatever meant to have a type parameter then?

[jeggy]

I have a complex repository pattern mixed with dependency injection. Where all repositories extend an interface `interface Repository<C: Criteria<C>>.`I want to create a function that can return a type of Repository<Criteria<*>> , but I can't get this part to work.

[Youssef Shoaib [MOD]]

And do you expect the callsite to be able to access class-specific properties like .data? Because if so there is kind of a solution