I'm sure there is an elegant way to convert this `...

# getting-started

[df]

I'm sure there is an elegant way to convert this

val catalogues = mapOf(
    "de-catalogue" to listOf(29L, 10010L, 10012L, 10013L),
    "fr-catalogue" to listOf(10007L, 10019L, 10020L),
    "nl-catalogue" to listOf(10008L, 10023L, 10024L),
    "it-catalogue" to listOf(10021L),
    "es-catalogue" to listOf(10022L)

into a Map<Long,String> where each list value becomes the key and the key (from the original map) becomes the value

[df]

catalogues.map { entry ->
    entry.value.associateWith { entry.key }
}

gives me a List<Map<Long,String>> but obviously I don't want to have a list of maps but only one map with all keys / values (bearbeitet)

[df]

catalogues.flatMap { entry ->
    entry.value.associateWith { entry.key }.asIterable()
}
.associate { it.key to it.value }

produces the expected result... but if someone has a cleaner approach, feel free to let me know

[karelpeeters]

_catalogues_._flatMap_ *{* (k, values) *->* values._map_ *{ it* _to_ k *} }*._groupBy_(*{ it*.first *}*, *{ it*.second *}*)

[df]

that will produce Map<Long,List<String>> instead of Map<Long, String>

[karelpeeters]

Ah that's easier:
_reversed_ = _catalogues_._flatMap_ *{* (k, values) *->* values._map_ *{ it* _to_ k *} }*._toMap_()

[df]

values.map { it to k } would do exactly the same as it.associateWith { k }

[karelpeeters]

No? Map returns a list while associate returns a map.

[df]

that's why i said "i always thought" 😉

[karelpeeters]

Just blame slack!