Hi All, Can somebody explain me how and why the ma...

# announcements

[Pablo Schmid]

Hi All, Can somebody explain me how and why the map function is working with the element instead of the optional?

-.kt

[Pablo Schmid]

Why do I need the it as Snapshot to make ir work?

[Czar]

because if you check, it is the Optional#map, not Kotlin map, this is because member method always takes preference over extension function with the same name and signature. Optional happens to have map method with the same signature as Kotlin map, so the former is used.
As to why you need the cast, check what your snapshotRepo#save returns.

[Pablo Schmid]

Thanks. Got the first part. Don’t really get why I need the it as snapshot. If I remove that part, the orElse(null) says “found nothing? requires Snapshot”

[Czar]

What does your repository return from the save method?

[Pablo Schmid]

a Snapshot

[Czar]

Are you sure? In that case it should work, does for me.

[Pablo Schmid]

it works but the orElse(null) says “found nothing? requires Snapshot” (edited) . It’s a warning

[Czar]

can you screenshot quickdoc of the save method?

[Pablo Schmid]

“/**
* Saves a given entity. Use the returned instance for further operations as the save operation might have changed the
* entity instance completely.
*
* @param entity must not be {@literal null}.
* @return the saved entity will never be {@literal null}.
*/
<S extends T> S save(S entity);”

[Pablo Schmid]

Im using a CrudRepository<Snapshot, UUID>

[Czar]

Ah, ok... strange let me think about it for a sec.

[Pablo Schmid]

Sure, Don’t worry. I was just curious about why I need the casting

[Czar]

you should not need the cast. Something weird is going on here

[Czar]

Ok, I've created a small test project with your code and I don't see any warnings

[Czar]

import org.springframework.data.repository.CrudRepository
import java.util.*

fun main() {
	lateinit var snapshotRepo: SnapshotRepo
	fun setSnapshotName(snapshotId: UUID, name: String): Snapshot? {
		val optional: Optional<Snapshot> = snapshotRepo.findById(snapshotId)
		return optional
			.map { it.name = name; snapshotRepo.save(it) }
			.orElse(null)
	}
	setSnapshotName(UUID.randomUUID(), "Test")
}

interface SnapshotRepo : CrudRepository<Snapshot, UUID>

class Snapshot {
	var name: String = ""
}

[Pablo Schmid]

Thanks a lot for your time Alexander. I will check in runtime what happens but yes, I agree that the cast should not eb necessary.