ios - Async task don't change external variable. Swift 3 -

i can't save data url, because function in infinit loop. how fix it? code:

func getregion2(){     let method = "region/"      var url = serviceurl+method     var myarray: [string]()     while(url != nil){          alamofire.request(url).validate().responsejson { response in             switch response.result {             case .success(let data):                  let nexturl = json(data)["next"].stringvalue                 url = nexturl                 myarray = myarray + myarray                 print(nexturl)              case .failure(let error):                 print("request failed error: \(error)")             }         }     }     print(myarray) } 

if run without "while", works fine.

one possible solution combine recursive function , dispatch group (not tested):

func getregion2(){     let method = "region/"      var url = serviceurl+method     var myarray: [string] = []      let group = dispatchgroup()      func getregion(with url: string) {         group.enter()         alamofire.request(url).validate().responsejson { response in             switch response.result {             case .success(let data):                  let nexturl = json(data)["next"].stringvalue                 myarray = myarray + somearrayfromrespnse                 print(nexturl)                  if nexturl != nil {                     getregion(with: nexturl)                 }                  group.leave()             case .failure(let error):                 print("request failed error: \(error)")             }         }     }      getregion(with: url)      group.notify(queue: dispatchqueue.main) {          print(myarray)     } } 

i use completionblock:

func getregion2(completion: () -> [string]?) {     let method = "region/"     var url = serviceurl+method     var myarray: [string] = []      func getregion(with url: string) {         alamofire.request(url).validate().responsejson { response in             switch response.result {             case .success(let data):                  let nexturl = json(data)["next"].stringvalue                 myarray = myarray + somearrayfromrespnse                 print(nexturl)                  if nexturl != nil {                     getregion(with: nexturl)                 } else {                     completion(myarray)                 }              case .failure(let error):                 completion(nil)             }         }     }      getregion(with: url) }