Any suggestions for the right approach to generics here?

import androidx.lifecycle.MutableLiveData

class ClearableLiveData<T> : MutableLiveData<Clearable<T>>() {
    fun clear(t: T) {
        super.postValue(Clearable.Clear)
        super.postValue(Clearable.Value(t))
    }
}

sealed class Clearable<T> {
    object Clear: Clearable<Any>()
    data class Value<T>(val t: T): Clearable<T>()
}

The first call to

super.postValue

gives a type mismatch

Clearable<Any> expects a type parameter; but since it's a singleton object you'll need Nothing because Nothing is a child of everything.

the out is important too though. without it

Clearable<Nothing>

isn't a subtype of

Clearable<T>

@Kroppeb could you explain that part any more? i don't quite understand it

You might wanna start reading here https://kotlinlang.org/docs/reference/generics.html

i have - is my assumption above incorrect? @Kroppeb

Since we are using

out T

, any of the type parameters can be a subtype of

T

, which

Nothing

is a subtype of everything.

ok so almost had that one then