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，该数组具有从给定数组中随机生成的数组组:

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
    }
}

我是这样使用它的:

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

它会打印成这样:

[[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我一个错误:

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

上面写着:

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 中无法运行。

我不知道怎么解决。

Answer 1

您正在尝试将一个元素与其自身交换，您将需要执行检查以查看您是否没有尝试将一个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
    }
}