NEW: Join my free 100 Days of SwiftUI challenge today! >>

Variadic functions

Some functions are variadic, which is a fancy way of saying they accept any number of parameters of the same type. The print() function is actually variadic: if you pass lots of parameters, they are all printed on one line with spaces between them:

print("Haters", "gonna", "hate")

You can make any parameter variadic by writing ... after its type. So, an Int parameter is a single integer, whereas Int... is zero or more integers – potentially hundreds.

Inside the function, Swift converts the values that were passed in to an array of integers, so you can loop over them as needed.

To try this out, let’s write a square() function that can square many numbers:

func square(numbers: Int...) {
    for number in numbers {
        print("\(number) squared is \(number * number)")
    }
}

Now we can run that with lots of numbers just by passing them in separated by commas:

square(numbers: 1, 2, 3, 4, 5)

LEARN SWIFTUI FOR FREE I have a massive, free SwiftUI video collection on YouTube teaching you how to build complete apps with SwiftUI – check it out!

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: 4.9/5