这是一些在playground上运行的代码。你不需要在实际的Xcode项目中导入Darwin。

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)

在Swift 3中，如果你想洗牌一个数组，或者从一个数组中获得一个新的洗牌数组，AnyIterator可以帮助你。其思想是从数组中创建一个索引数组，用AnyIterator实例和swap(_:_:)函数洗牌这些索引，并将AnyIterator实例中的每个元素映射到数组的相应元素。

下面的Playground代码展示了它是如何工作的:

import Darwin // required for arc4random_uniform

let array = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
var indexArray = Array(array.indices)
var index = indexArray.endIndex

let indexIterator: AnyIterator<Int> = AnyIterator {
    guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
        else { return nil }

    index = nextIndex
    let randomIndex = Int(arc4random_uniform(UInt32(index)))
    if randomIndex != index {
        swap(&indexArray[randomIndex], &indexArray[index])
    }

    return indexArray[index]
}

let newArray = indexIterator.map { array[$0] }
print(newArray) // may print: ["Jock", "Ellie", "Sue Ellen", "JR", "Pamela", "Bobby"]

你可以重构前面的代码，并在Array扩展中创建一个shuffled()函数，以便从数组中获得一个新的洗牌数组:

import Darwin // required for arc4random_uniform

extension Array {

    func shuffled() -> Array<Element> {
        var indexArray = Array<Int>(indices)        
        var index = indexArray.endIndex

        let indexIterator = AnyIterator<Int> {
            guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
                else { return nil }

            index = nextIndex                
            let randomIndex = Int(arc4random_uniform(UInt32(index)))
            if randomIndex != index {
                swap(&indexArray[randomIndex], &indexArray[index])
            }

            return indexArray[index]
        }

        return indexIterator.map { self[$0] }
    }

}

用法:

let array = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
let newArray = array.shuffled()
print(newArray) // may print: ["Bobby", "Pamela", "Jock", "Ellie", "JR", "Sue Ellen"]

let emptyArray = [String]()
let newEmptyArray = emptyArray.shuffled()
print(newEmptyArray) // prints: []

作为前面代码的替代方案，您可以在Array扩展中创建一个shuffle()函数，以便在适当的位置洗牌数组:

import Darwin // required for arc4random_uniform

extension Array {

    mutating func shuffle() {
        var indexArray = Array<Int>(indices)
        var index = indexArray.endIndex

        let indexIterator = AnyIterator<Int> {
            guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
                else { return nil }

            index = nextIndex                
            let randomIndex = Int(arc4random_uniform(UInt32(index)))
            if randomIndex != index {
                swap(&indexArray[randomIndex], &indexArray[index])
            }

            return indexArray[index]
        }

        self = indexIterator.map { self[$0] }
    }

}

用法:

var mutatingArray = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
mutatingArray.shuffle()
print(mutatingArray) // may print ["Sue Ellen", "Pamela", "Jock", "Ellie", "Bobby", "JR"]

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

你也可以使用通用交换函数，实现前面提到的Fisher-Yates:

for idx in 0..<arr.count {
  let rnd = Int(arc4random_uniform(UInt32(idx)))
  if rnd != idx {
    swap(&arr[idx], &arr[rnd])
  }
}

或者更简洁:

for idx in 0..<steps.count {
  swap(&steps[idx], &steps[Int(arc4random_uniform(UInt32(idx)))])
}

当我将xCode版本升级到7.4 beta时，它停止在“swap(&self[i]， &self[j])”。 致命错误:不支持与自身交换位置

我找到了I = j的原因(交换函数将爆炸)

所以我添加了一个条件，如下所示

if (i != j){
    swap(&list[i], &list[j])
}

丫!对我来说没问题。

这里有一些可能更短的内容:

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