is there a variant of `associateBy` that would thr...

# getting-started

[poohbar]

is there a variant of associateBy that would throw if a key should have more than one value?

[tseisel]

You could write such an extension :

inline fun <T, K> Iterable<T>.associateUniquelyBy(crossinline keyProvider: (T) -> K): Map<K, T> {
    return groupingBy(keyProvider).aggregate { key, accumulator, element, first ->
        if (first) element else error("Duplicated key: an element is already associated to the key $key")
    }
}