How to split an array into chunks

Swift version: 5.1

Paul Hudson    @twostraws    May 28th 2019

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

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