I am migrating codebase from Rx1 to Rx2 and now that `null` is not supported by RxJava and RxKotlin,...

# announcements

[aaverin]

I am migrating codebase from Rx1 to Rx2 and now that null is not supported by RxJava and RxKotlin, what is the strategy you use to have kind of null values?
We have some places in codebase that were doing something like

map {
  service.get() //can return null
}.filterNotNull()

It's too much effort to rewrite every service to not ever return null when before null was considered a valid empty value.

[aaverin]

Using Java Optional in Kotlin kind of makes me shiver.

[jw]

We use Koptional from Juno. I don't see a problem with using an optional abstraction in Kotlin: https://developer.squareup.com/blog/an-optionals-place-in-kotlin/

[pawegio]

You can declare your own Optional

data class Optional<out T>(val value: T?)

val <T> T?.optional get() = Optional(this)

fun <T> Observable<T>.startWithNull(): Observable<Optional<T>> = map { it.optional }.startWith(null.optional)
fun <T> Observable<Optional<T>>.filterNotNull(): Observable<T> = filter { it.isNotNull }.map { it.value!! }

[aaverin]

Feels like I should rather go to Coroutines than RxJava 2, but the codebase is far from being ready for that

[jw]

Yep, Flow is a good choice.