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How to shuffle an array in iOS 8 and below

Written by Paul Hudson    @twostraws

Nate Cook wrote a simple shuffle() extension to arrays that implements the Fisher-Yates shuffle algorithm in Swift. I use it a lot, or at least did until GameplayKit came along in iOS 9.0 – it has its own shuffle algorithm, and so is preferable.

If you're stuck on iOS 8.0 or below, here's the code:

extension Array {
    mutating func shuffle() {
        for i in 0 ..< (count - 1) {
            let j = Int(arc4random_uniform(UInt32(count - i))) + i
            swapAt(i, j)
        }
    }
}

Available from iOS 2.0 – see Hacking with Swift tutorial 35

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