How to create proper completion handler for server login in swift? - swift

Question

I have an api manager class in my swift application and it has a server login with username and password.
I want to know how to create a completion handler for it that when the server responses with 200 status code, the function handles that response and for example performs a segue in the viewcontroller.
I did not find any tutorials for this. Thanks for your help!
EDIT 1:
What i need is: The completion handler is immediately run when the function is called. I want the completion handler run after server responds.
And this is my login function:
public class func Login(username: String, password: String, complitionHandler: #escaping (Int) -> Void) {
let urlS = "http://server.com/" + "login.php"
let url = URL(string: urlS)
var request = URLRequest(url: url!)
request.httpMethod = "POST"
let body = "username=\(username.lowercased())&password=\(password)"
request.httpBody = body.data(using: .utf8)
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
guard let data = data, error == nil else {
print(error!)
print("error")
logedIn = 2
return
}
do{
let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? NSDictionary
if let parseJson = json {
let code = parseJson["status"] as! String
if code == "200" {
print("loged inn")
logedIn = 1
}else if code == "400" {
print("uuuser/pass error")
logedIn = 0
}
}
}catch{
print("json error")
logedIn = 2
}
}
task.resume()
DispatchQueue.main.async {
complitionHandler(logedIn)
}
}
And how i call the function in my ViewController:
Manager.Login(username: "1", password: "1") { (i) in
switch i {
case 0:
print("user/pass error")
case 1:
print("loged in")
self.performSegue(withIdentifier: "toMain", sender: self)
case 2:
print("json error")
default:
()
}
}

Answer 1

You have all of the pieces in place. You just need to move your call to the completion handler to the correct place:
}catch{
print("json error")
logedIn = 2
}
DispatchQueue.main.async {
complitionHandler(logedIn)
}
}
task.resume()
Also note that method names should start with lowercase letters so your Login function should be named login.
Now you can use this login method like:
login(username: someUsername, password: somePassword) { (result) in
if result == 1 {
// success - do your segue
} else if result == 0 {
// bad username/password
} else {
// some error
}
}