fatal error: swapping a location with itself is not supported with Swift 2.0

I have this extension which will create a new array which have group of arrays randomly from given array:

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
    }
}

And I am using it like this:

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

    And it will print like:

    [[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]]
    

    But it is giving me an error at run time at this line:

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

    Which says:

    fatal error: swapping a location with itself is not supported

    It was working fine in 1.2 but now it is not working in 2.0.

    I don’t know how to solve this.

    Solutions Collect From Internet About “fatal error: swapping a location with itself is not supported with Swift 2.0”

    You are trying to swap an element with itself, you will need to perform a check to see if you are not trying to swap an element to the same spot in the array, like so:

    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
        }
    }