NEW: Learn to build amazing SwiftUI apps for macOS with my new book! >>

Generating random numbers with GameplayKit: GKRandomSource

Let's look at the most basic way of generating random numbers using GameplayKit, which is the GKRandomSource class and its sharedRandom() method. Of course, this means adding an import for GameplayKit into the playground, so please do that now.

A random source is a provider of an unfiltered stream of random numbers as you need them. As you'll see soon, GameplayKit has various options for your stream, but for now we're going to look at the simplest one: sharedRandom().

Using sharedRandom() for a random number source returns the systems built-in random source that's used for a variety of other tasks, which means you can be pretty sure it's in a truly random state by the time it gets to you. It does, however, mean that it's useless for synchronizing network games, because everyone's device is in a different state.

To produce a truly random number you'd use the nextInt() method like this:


That produces a number between -2,147,483,648 and 2,147,483,647 – yes, that's a negative number, which means it's not a drop-in replacement for arc4random(). Plus, even with GameplayKit's great new logic, Apple includes a warning that it's not guaranteed to be random for very specific situations, so for both these reasons it's not likely you'll want to use nextInt() much.

As an alternative, try using the nextInt(upperBound:) method, which works identically to arc4random():

print(GKRandomSource.sharedRandom().nextInt(upperBound: 6))

That will return a random number from 0 to 5 using the system's built-in random number generator.

As well as nextInt() and nextInt(upperBound:) are nextBool() for generating a random true/false value and nextUniform() for generating a random floating-point number between 0 and 1. Both of these are implemented using nextInt(upperBound:) so they output properly random numbers.

Note: If you’re just generating simple random values, using Swift’s Int.random(in:), Float.random(in:), Double.random(in:), and Bool.random() are much easier than using GameplayKit. However, GameplayKit does have the advantage that you can shape its random output, as we’ll look at next…

Hacking with Swift is sponsored by Fernando Olivares

SPONSORED Fernando's book will guide you in fixing bugs in three real, open-source, downloadable apps from the App Store. Learn applied programming fundamentals by refactoring real code from published apps. Hacking with Swift readers get a $10 discount!

Read the book

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

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: 5.0/5

Unknown user

You are not logged in

Log in or create account

Link copied to your pasteboard.