NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

How to use reduce() to condense an array into a single value

Swift version: 5.2

Paul Hudson    @twostraws   

The reduce() method iterates over all items in array, combining them together somehow until you end up with a single value. The “somehow” is specified by a closure you provide, for example you might want to count how many characters are provided in an array of names, which looks like this:

let names = ["Taylor", "Paul", "Adele"]
let count = names.reduce(0) { $0 + $1.count }
print(count)

That starts with a total of 0 (the parameter passed in to reduce(), then adds that to the count of each string in the array. So, it starts by adding 6 for Taylor (so the running total is 6), then adds 4 for Paul (so the running total is 10), then adds 5 more for Adele (so the running total is 15.)

Hacking with Swift is sponsored by Instabug

SPONSORED Are you tired of wasting time debugging your Swift app? Instabug’s SDK is here to help you minimize debugging time by providing you with complete device details, network logs, and reproduction steps with every bug report. All data is attached automatically, and it only takes a line of code to setup. Start your free trial now and get 3 months off exclusively for the Hacking with Swift Community.

Start your free trial!

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS – learn more in my book Pro Swift

Similar solutions…

About the Swift Knowledge Base

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

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.7/5

Link copied to your pasteboard.