Am I correct that using 1.4 the correct replacement of `x.maxBy { ...}!!` is `x.maxByOrNull { ...}!...

# announcements

[Paul Woitaschek]

Am I correct that using 1.4 the correct replacement of x.maxBy { ...}!! is x.maxByOrNull { ...}!! and that there is no replacement that throws if the result is null?

[Big Chungus]

maxOf throws, maxOfOrNull returns null

[Paul Woitaschek]

I meant maxBy

[Big Chungus]

Yeah, me too 😄

[Big Chungus]

x.maxBy { ...}!! is redundant as it'll never return null

[Paul Woitaschek]

Yes, it will, it's nullable

[Paul Woitaschek]

I.e if we have:

fun test() {
  data class Person(val age: Int)
  val oldestPerson: Person = listOf(Person(42), Person(12))
    .maxBy { it.age }!!
}

[Paul Woitaschek]

Thats deprecated (and still nullable)

@Deprecated("Use maxByOrNull instead.", ReplaceWith("maxByOrNull(selector)"))
@DeprecatedSinceKotlin(warningSince = "1.4")
public inline fun <T, R : Comparable<R>> Iterable<T>.maxBy(selector: (T) -> R): T? {
    return maxByOrNull(selector)
}

[Big Chungus]

My bad, maxBy is now deprecated. In that case there's no throwing option other than just x.maxByOrNull { ...}!!

[Big Chungus]

Which means you were correct all along and I was just leading you astray 😄

[Paul Woitaschek]

There is maxOf but that returns the type of the lambda

[Paul Woitaschek]

And it throws a NoSuchElementException which is what I want. In these cases a NPE isn't hiding the underyling fact that I want to get sth from the list thats not there

[Big Chungus]

x.maxByOrNull { ...} ?: throw MyAwesomeError()?

[arekolek]

It should come in 1.6 as far as I know https://youtrack.jetbrains.com/issue/KT-38854

[Sam Garfinkel]

If this is a common pattern in your code, you can easily implement a function for it yourself as @Big Chungus suggested.

[Paul Woitaschek]

The missing link was the ticket posted by @arekolek without that the whole change made no sense for me. I expect that there will be an inspection with a quick fix once 1.6 hits