If I have: ```interface Cacheable { ...

# getting-started

[dave08]

If I have:

interface Cacheable {

                                                               v This is an error... R needs to inherit from Any... but I'd like R to OPTIONALLY be nullable
    suspend operator fun <R> invoke(name: String, type: KClass<R>, vararg params: Any, block: suspend () -> R): R =
        cache(name, type, *params, block = block)
}

Where it's being used, R could be nullable or not nullable so I can't just use R? and <R: Any>... what other options do I have?

[Joffrey]

Use KClass<R & Any>?

[dave08]

That seems to not make the IDE complain, except for this:

suspend inline fun <reified R> Cacheable.cache(
    name: String,
    vararg params: Any,
    noinline block: suspend () -> R
): R =
    cache(name, R::class, *params, block = block)

cache is defined the same as invoke...

[Joffrey]

Yeah because R::class cannot work if R is nullable

[dave08]

Any way to pass it down to suspend fun <R> cache(name: String, type: KClass<R & Any>, vararg params: Any, block: suspend () -> R): R ?

[dave08]

On the call site:

fun foo(): Something? = cache("name") { ... }

[dave08]

If Something is returned, I need KotlinX serialization to be able to transform it to json... if not, then I don't need the KClass at all...

[Joffrey]

Did you try passing down the serializer instead of the KClass? Maybe the reified serializersModule.serializer<T>() is more lenient with nullable types:
https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-core/kotlinx.serialization/serializer.html

[dave08]

Thanks! I'll give that a try.

[dave08]

It works nicely, thanks again!

[Joffrey]

Good to hear!