NEW: Master Swift design patterns with my latest book! >>

How to find the index of the first matching array element

Written by Paul Hudson    @twostraws

If you have an array of items and want to find the first item that matches a specific condition, you should use the index(where:) method. This accepts a closure of code to use as a test, applies that test to all elements in an array, then returns the index of the first item to match it. If no item matches you’ll get back nil, so be prepared to unwrap the optional you get sent back.

For example, if we had an array of numbers:

let numbers = [2, 4, 6, 8, 9, 10]

We could find the first odd number like this:

let firstOdd = numbers.index { $0 % 2 == 1 }

That will send back 4 as an optional integer, because the first odd number (9) is at index four.

Available from iOS 8.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Master iOS 11 now!

My book Practical iOS 11 gives you seven complete coding projects that teach all the major new features in iOS 11 in a smart, practical way.

Click here to visit the Hacking with Swift store >>