How do I shuffle an array in Swift?

Question

How do I randomize or shuffle the elements within an array in Swift? For example, if my array consists of 52 playing cards, I want to shuffle the array in o

Answer 1

In SWIFT 4

func createShuffledSequenceOfNumbers(max:UInt)->[UInt] {

    var array:[UInt]! = []
    var myArray:[UInt]! = []
    for i in 1...max {
        myArray.append(i)
    }
    for i in 1...max {
        array.append(i)
    }
    var tempArray:[Int]! = []
    for index in 0...(myArray.count - 1) {

        var isNotFinded:Bool = true
        while(isNotFinded){

            let randomNumber = arc4random_uniform(UInt32(myArray.count))
            let randomIndex = Int(randomNumber)

            if(!tempArray.contains(randomIndex)){
                tempArray.append(randomIndex)

                array[randomIndex] = myArray[index]
                isNotFinded = false
            }
        }
    }

    return array
}

Answer 2

Swift 3 solution, following @Nate Cook answer: (work if the index starts with 0, see comments below)

extension Collection {
    /// Return a copy of `self` with its elements shuffled
    func shuffle() -> [Generator.Element] {
        var list = Array(self)
        list.shuffleInPlace()
        return list
    } }

extension MutableCollection where Index == Int {
    /// Shuffle the elements of `self` in-place.
    mutating func shuffleInPlace() {
        // empty and single-element collections don't shuffle
        if count < 2 { return }
        let countInt = count as! Int

    for i in 0..<countInt - 1 {
        let j = Int(arc4random_uniform(UInt32(countInt - i))) + i
            guard i != j else { continue }
            swap(&self[i], &self[j])
        }
    }
}

Answer 3

Here's some code that runs in playground. You won't need to import Darwin in an actual Xcode project.

import darwin

var a = [1,2,3,4,5,6,7]

func shuffle<ItemType>(item1: ItemType, item2: ItemType) -> Bool {
    return drand48() > 0.5
}

sort(a, shuffle)

println(a)

Answer 4

Here's something possibly a little shorter:

sorted(a) {_, _ in arc4random() % 2 == 0}

Answer 5

In Swift 4.2, there is now a method for both a mutable shuffle and immutable shuffled. You can read more about the random generation and array stuff here.

Answer 6

let shuffl = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: arrayObject)