How to sum an array of numbers using reduce()

Paul Hudson    February 12th 2018    @twostraws

The reduce() method is designed to convert a sequence into a single value, which makes it perfect for calculating the total of an array of numbers.

For example, given the following number array:

let numbers = [1, 12, 2, 9, 27]

We could calculate the total of all those numbers like this:

let total = numbers.reduce(0, +)

The first parameter passed to reduce() is the value it should start with, in this case 0. The second parameter is how it should combine that 0 with each item in your array, which means it will do 0 + 1 to make 1, then 1 + 12 to make 13, and so on.

Available from iOS 8.0

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

Tweet

Other people are reading…

• What are keypaths?
• What is optional chaining?
• How to fix the error “protocol can only be used as a generic constraint because it has Self or associated type requirements”
• How to find the minimum of three numbers
• What are class and subtype existentials?

About the Swift Knowledge Base

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