SALE: Save 50% on all my books and bundles >>

How to shuffle an array using arc4random_uniform()

Swift version: 5.1

Paul Hudson    @twostraws   

Modern Swift code will use Swift’s own shuffle() and shuffled() methods, but sometimes you might find code that does it by hand using arc4random_uniform() or similar.

Nate Cook wrote a simple shuffle() extension to arrays that implements the Fisher-Yates shuffle algorithm in Swift. Here's the code:

extension Array {
    mutating func customShuffle() {
        for i in 0 ..< (count - 1) {
            let j = Int(arc4random_uniform(UInt32(count - i))) + i
            swapAt(i, j)
        }
    }
}
Hacking with Swift is sponsored by Instabug

SPONSORED Catch bugs as soon as they happen and know exactly why a crash occurred by integrating Instabug's SDK in one minute. You will automatically receive device data, network logs, and reproduction steps with every bug and crash report.

Learn more and get started for free

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

Snapthread is a casual video editor and slideshow maker that makes discovering, compiling and sharing your favorite memories effortless.

Available from iOS 2.0 – see Hacking with Swift tutorial 35

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!