is there any kind of multi-key

associate { }

function that I’m missing? I’m trying to build a map and have multiple keys associated with the objects I’m iterating over - currently I’ve got something like this:

entries.flatMap { entry ->
      (entry.aliases + entry.name).map { it to entry }
}.toMap()

which probably isn’t the most efficient approach 😬

Honestly, not sure what type entries is but I'm guessing you want something similar to

entries.associateBy( {it.name to it.aliases}, {it} )

No his example code maps the key

entry.name

and the keys

entry.aliases

all to the same value

entry

.

Hmm, do you want a list of strings as key with the entry as the value or do you want all strings in list to be a separate key. If its the former, then

entries.associateBy { it.keys }

If you meant the latter then I guess,

entries.fold(emptyList<String>()) { sum, element ->
        sum + element.keys
    }.associateWith { key -> entries.find { entry -> entry.keys.contains(key) } }

also

data class Entry(val name: String, val aliases: List<String>) {
        val keys = (listOf(name) + aliases).toSet()
    }

That has even worse performance though,

fold { find { contains } }

!