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

Question

I can't save data from URL, because function in infinit loop. How fix it?
My 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 with error: \(error)")
}
}
}
print(myArray)
}
If run without the "while", then everything works fine.

Answer 1

One possible solution is to combine a recursive function and a 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 with error: \(error)")
}
}
}
getRegion(with: url)
group.notify(queue: DispatchQueue.main) {
print(myArray)
}
}
I would use a 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)
}