I want to find an item in a list. When I find it, ...

# getting-started

[Colton Idle]

I want to find an item in a list. When I find it, I also want the index of it.

I have found

list.indexOfFirst

and

list.first

but is there some way to get both?

[ephemient]

list.withIndex().first { predicate(it.value) }

[Albert Chang]

If your list is a random access list (such as ArrayList), getting the index and then retrieving the value using the index is more efficient as the access is O(1) and there’s no additional object allocations which isn’t the case when using withIndex().

[ephemient]

this is true, and almost every list you will commonly encounter except LinkedList is RandomAccess

[Colton Idle]

So theres basically no way to do it in one call (what Albert is recc'ing)? Basically just find the index first, then grab the item with said index. No fancy idiomatic kotlin function or something available?

[ephemient]

you could put a nice wrapper around

val (index, value) = run {
    list.forEachIndexed { index, value ->
        if (predicate(value)) return@run IndexedValue(index, value)
    }
    throw NoSuchElementException()
}

or something, but otherwise, pick fast (indexOf) or concise (withIndex)

[Colton Idle]

fast it is! Glad I wasn't missing any cool function I just didn't stumble upon, but I did TIL withIndex
Thanks as always @ephemient and @Albert Chang