How to split an array into chunks

Written by Paul Hudson    @twostraws

If you have an array of elements and you want to split them into chunks of a size you specify, here’s a useful extension you can add to your code:

extension Array {
    func chunked(into size: Int) -> [[Element]] {
        return stride(from: 0, to: count, by: size).map {
            Array(self[$0 ..< Swift.min($0 + size, count)])
        }
    }
}

That converts an array into an array of arrays, using whatever size you specify. For example, if you have the numbers 1 to 100 in an array and you want to split it so that there are many arrays containing five numbers each, you’d write this:

let numbers = Array(1...100)
let result = numbers.chunked(into: 5)

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 a nested class or nested struct?
• How to write a closure that returns a value
• How to make a number positive using abs()
• How to fix the error “protocol can only be used as a generic constraint because it has Self or associated type requirements”

About the Swift Knowledge Base

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