NEW: Master Swift design patterns with my latest book! >>

How to make a variadic function

Written by 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 sum(_ 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 sum(_ 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 = sum(1, 2, 3, 4, 5)

Available from iOS 8.0 – learn more in my book Pro Swift

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

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

Test your Swift today

Think you know Swift? My book Swift Coding Challenges will put your Swift skills to the test – it's perfect for job interviews and more!

Click here to visit the Hacking with Swift store >>