Swift 3: get information from server in ViewDidLoad and when click a button, wait for information response from server

Question

In my app, I want to call an async function (using alamofire) in ViewDidLoad, and user can still interact with the view until he presses a button, and I want the app to show progress hud if the async function is not finished or go to next view if it's finished. I don't want to call the async function on button click, because it may take sometimes and user has to wait longer compare to I call the async function at ViewDidLoad How can I do this?

Answer 1

Edit - use enum to hold the view controller state

enum State {
    case Loading
    case Ready
    case ShowNext
}
var state: State

func viewDidLoad() {
  state = .Loading
  makeAsyncCall() { (finished) in 
     if state == .ShowNext {
         showNext()
     } else {
         state = .Ready
     }
 }

}

func buttonTapped() {
 if state == .Ready {
    showNext()
 } else {
    state = .ShowNext
 }
}