How to correct the order of execution of code in Swift 5? - swift5

Question

The code within the function is executed in a different order than it is expected. I wanted to change the state of the login Boolean variable inside the if statement, but the function returns the initial value before if statement is completed.
Code sample:
class ClassName {
func loginRequest (name: String, pwd: String) -> Bool {
var login:Bool
//Initial value for login
login = false
let task = session.uploadTask(with: request, from: jsonData) { data, response, error in
if let httpResponse = response as? HTTPURLResponse {
print(httpResponse.statusCode)
if (httpResponse.statusCode) == 200 {
//Change the value of login if login is successful
login = true
if let data = data, let dataString = String(data: data, encoding: .utf8) {
do {
...
} catch {print(error.localizedDescription)}
}
}
}
}
task.resume()
//Problem return false in any case because return is completed before if statement
return login
}
}

Answer 1

Completion Handlers is your friend
The moment your code runs task.resume(), it will run your uploadTask and only when that function is finished running it will run the code where you change your login variable.
With That said: That piece of code is running asynchronously. That means your return login line of code won't wait for your network request to come back before it runs.
Your code is actually running in the order it should. But i myself wrote my first network call like that and had the same problem. Completion Handles is how i fixed it
Here is a very nice tutorial on Completion Handlers or you might know it as Callbacks :
Link To Completion Handlers Tutorial
If i can give you a little hint - You will have to change your function so it looks something like this: func loginRequest (name: String, pwd: String, completionHandler: #escaping (Bool) -> Void)
And replace this login = true with completionHandler(true)
Wherever it is you call your function it will look something like this:
loginRequest(name: String, pwd: String) {didLogIn in
print("Logged In : \(didLogIn)")
}
One last thing... You're actually already using Completion Handlers in your code.
let task = session.uploadTask(with: request, from: jsonData) { data, response, error in
... ... But hopefully now you understand a little bit better, and will use a completion handler approach when making network calls.
GOOD LUCK !