UPGRADE YOUR SKILLS: Learn advanced Swift and SwiftUI on Hacking with Swift+! >>

How to make a variadic function

Swift version: 5.6

Paul Hudson    @twostraws   

Variadic functions are functions that accept any number of parameters. The most common one in Swift is print() – most people use it to print a single value, but you can actually pass as many as you want, like this:

print(1, 2, 3, 4, 5)

To make a variadic function of your own, just add ... after any parameter. For example, we could write a sum() function that accepts any number of integers and adds them together, like this:

func sum1(_ numbers: Int...) -> Int {
    var total = 0

    for number in numbers {
        total += number
    }

    return total
}

Or if you wanted to write that functionally, you would use reduce():

func sum2(_ numbers: Int...) -> Int {
    return numbers.reduce(0, +)
}

Notice how we specify Int... rather than Int – that means this function can be called using no integers, one integer, or even a hundred integers, and Swift will automatically convert them to be an array of integers inside the function.

So, it would be called like this:

let total = sum2(1, 2, 3, 4, 5)
Hacking with Swift is sponsored by RevenueCat

SPONSORED Take the pain out of configuring and testing your paywalls. RevenueCat's Paywalls allow you to remotely configure your entire paywall view without any code changes or app updates.

Learn more here

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

Available from iOS 8.0 – 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 Pro SwiftUI 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 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 Beyond Code

Was this page useful? Let us know!

Average rating: 3.0/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.