Is there already a more idiomatic way to do this (...

# codingconventions

[darkmoon_uk]

Is there already a more idiomatic way to do this (which is at least as efficient?):

fun <T,R> Iterable<T>.firstMappedOrNull( mapping: (T)->R? ) : R? {
    for(element in this) {
        mapping(element)?.let { return it }
    }
    return null
}

[rook]

foo.map { /*some transform*/ }.find { it != null }

[marstran]

Using a sequence:

return asSequence()
  .map(mapping)
  .find { it != null }

[marstran]

I think the null check has to be on the result of the call to mapping @rook

[rook]

Ah, I didn’t realize that, good catch

[Yossi Saiada]

foo.mapNotNull(mapping).firstOrNull()

[darkmoon_uk]

@Yossi Saiada That is concise but less efficient - in your solution all values will be mapped before the first is picked.
@marstran’s solution addresses that requirement with a Sequence - where sequence operators generally act like builders, deferring computation of each element until there's an operator that forces the value to resolve e.g. .toList().