DispatchGroup with async task - swift

Question

enter code hereI try lot of thing with the dispatch group but I can't obtain stable result.
I use Alamofire for get data since my server. I've write a function in the Helper Class and I use this function in AppDelegate.swift.
I don't know if I put the dispatch group when I call the function so in AppDelegate or I put the dispatch group only in the function in Helper Class.
func alomofireGet(URL: String, onCompletion:#escaping ((JSON) -> Void)) {
// let group = DispatchGroup()
var contentJSON = JSON()
// group.enter()
Alamofire.request(URL, method: .get).responseJSON() { (reponse) in
if reponse.result.isSuccess {
contentJSON = JSON(reponse.result.value!)
} else {
contentJSON = JSON(reponse.result.error!)
}
// group.leave()
}
// group.notify(queue: .main) {
onCompletion(contentJSON)
}
In App delegate, I write a function who call the function in my class.
func connect() {
let group = DispatchGroup()
let _: Bool = KeychainWrapper.standard.removeObject(forKey: "token")
var token = String()
group.enter()
Helper().alomofireGet(URL: "http://192.168.1.19/app_dev.php/login/app") { contenuJSON in
token = contenuJSON["csrfToken"].stringValue
group.leave()
}
group.notify(queue: .main) {
let _: Bool = KeychainWrapper.standard.set(token, forKey: "token")
let t: String? = KeychainWrapper.standard.string(forKey: "token")
print(t!)
}
}
The problem is the variable "t" is empty.
And when I call the keychainWrapper in app delegate, the keychain is empty also.
PS : I have other task, I've just reduce my code

Answer 1

func alomofireGet(URL: String, onCompletion:#escaping ((JSON) -> Void)) {
// let group = DispatchGroup()
var contentJSON = JSON()
// group.enter()
Alamofire.request(URL, method: .get).responseJSON() { (reponse) in
if reponse.result.isSuccess {
contentJSON = JSON(reponse.result.value!)
} else {
contentJSON = JSON(reponse.result.error!)
}
// group.leave()
}
// group.notify(queue: .main) {// where you call wait()function. This blocks the current thread until the group’s tasks have completed.
onCompletion(contentJSON)
}

Answer 2

I try this but is not the solution. I've remove the function in my Helper. I'have juste this function in the app delegate.
func connect(onCompletion : #escaping (String) -> ()) {
let group = DispatchGroup()
var token = String()
let _: Bool = KeychainWrapper.standard.removeObject(forKey: "token")
group.enter()
Alamofire.request("http://192.168.1.19/app_dev.php/login/app", method: .get).responseJSON() { (reponse) in
if reponse.result.isSuccess {
let contentJSON = JSON(reponse.result.value!)
token = contentJSON["csrfToken"].stringValue
} else {
token = "Invalid Token"
}
group.leave()
}
group.notify(queue : DispatchQueue.global()) {
onCompletion(token)
}
}
when I print token, I have a empty message.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
Thread.sleep(forTimeInterval: 1.5)
connect() { token in
print(token)
}
return true
}