swift - fatal error : swapping a location with itself is not supported with Swift 2. 0

Question

我有这个扩展，它将创建一个新数组，其中包含来自给定数组的随机数组:

extension Array {
    var shuffle:[Element] {
        var elements = self
        for index in 0..<elements.count {
            swap(&elements[index], &elements[ Int(arc4random_uniform(UInt32(elements.count-index)))+index ])
        }
        return elements
    }
    func groupOf(n:Int)-> [[Element]] {
        var result:[[Element]]=[]
        for i in 0...(count/n)-1 {
            var tempArray:[Element] = []
            for index in 0...n-1 {
                tempArray.append(self[index+(i*n)])
            }
            result.append(tempArray)
        }

        return result
    }
}

我这样使用它:

let mainArr = Array(1...60)
let suffeldArr = mainArr.shuffle.groupOf(10)
print(suffeldArr)

它会打印如下:

[[10 random element between 1 to 60], [10 random element between 1 to 60], [10 random element between 1 to 60], [10 random element between 1 to 60], [10 random element between 1 to 60], [10 random element between 1 to 60]]

但它在运行时在这一行给了我一个错误:

swap(&elements[index], &elements[ Int(arc4random_uniform(UInt32(elements.count-index)))+index ])

其中说:

fatal error: swapping a location with itself is not supported

它在 1.2 中运行良好，但现在在 2.0 中不起作用。

我不知道如何解决这个问题。

Answer 1

您正在尝试将一个元素与其自身交换，您需要执行检查以查看您是否没有尝试将元素交换到数组中的同一位置，如下所示:

extension Array {
    var shuffle:[Element] {
        var elements = self
        for index in 0..<elements.count {
            let newIndex = Int(arc4random_uniform(UInt32(elements.count-index)))+index
            if index != newIndex { // Check if you are not trying to swap an element with itself
                swap(&elements[index], &elements[newIndex])
            }
        }
        return elements
    }
    func groupOf(n:Int)-> [[Element]] {
        var result:[[Element]]=[]
        for i in 0...(count/n)-1 {
            var tempArray:[Element] = []
            for index in 0...n-1 {
                tempArray.append(self[index+(i*n)])
            }
            result.append(tempArray)
        }

        return result
    }
}