swift2 - fatal error: swapping a location with itself is not supported with Swift 2.0 -

i have extension create new array have group of arrays randomly given array:

extension array {     var shuffle:[element] {         var elements = self         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]]=[]         in 0...(count/n)-1 {             var temparray:[element] = []             index in 0...n-1 {                 temparray.append(self[index+(i*n)])             }             result.append(temparray)         }          return result     } } 

and using this:

let mainarr = array(1...60) let suffeldarr = mainarr.shuffle.groupof(10) print(suffeldarr) 

and print like:

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

but giving me error @ run time @ line:

swap(&elements[index], &elements[ int(arc4random_uniform(uint32(elements.count-index)))+index ]) 

which says:

fatal error: swapping location not supported

it working fine in 1.2 not working in 2.0.

i don't know how solve this.

you trying swap element itself, need perform check see if not trying swap element same spot in array, so:

extension array {     var shuffle:[element] {         var elements = self         index in 0..<elements.count {             let newindex = int(arc4random_uniform(uint32(elements.count-index)))+index             if index != newindex { // check if not trying swap element                 swap(&elements[index], &elements[newindex])             }         }         return elements     }     func groupof(n:int)-> [[element]] {         var result:[[element]]=[]         in 0...(count/n)-1 {             var temparray:[element] = []             index in 0...n-1 {                 temparray.append(self[index+(i*n)])             }             result.append(temparray)         }          return result     } }