I'm going to groupby Set<Pair<String,Int>> values to Map<String, Set<Int>> so simply. Find all matching ints for string and create set. I've got solution that works:
setStringInt.stream()
.collect(
groupingBy(
Projection::stringObj,
mapping(Projection::intObj,
toSet<Int>())
)
)
I've got kind of cleaner:
.groupBy { it.stringobj }
.mapValues { it.value.map { it.intobj }.toSet() }
But it's looking quite dirty. Do you have any idea how to simplify this? Am I able to do this without using stream?
I think this is more readable:
setStringInt.groupBy({ it.first }, { it.second }).mapValues { it.value.toSet() }
using the
inline fun <T, K, V> Iterable<T>.groupBy(
keySelector: (T) -> K,
valueTransform: (T) -> V
): Map<K, List<V>>
overload.
You can just use the Kotlin functions groupBy and then mapValues directly on the Set.
You first use groupBy on it.first to get a Map<String, List<Pair<String, Int>>. Then you need to map the values of the resulting map, so you get a List<Int> from the List<Pair<String, Int>>. Like this:
setStringInt.groupBy { it.first }
.mapValues { entry -> entry.value.map { it.second }.toSet() }