致命错误:Swift 2.0不支持与自身交换位置

Question

我有这个扩展,它将创建一个新的数组,其中包含从给定数组中随机组的数组:

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)

它将打印如下:

[[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]]

但它在运行时给出了一个错误:

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

哪个说:

致命错误:不支持与自身交换位置

它在1.2中运行良好,但现在它在2.0中不起作用.

我不知道如何解决这个问题.

Answer 1

您正在尝试将元素与自身交换,您需要执行检查以查看您是否尝试将元素交换到数组中的相同位置,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
    }
}