UIAlertController not displaying immediately - ios

Question

I'm new to Swift programming, but can't find an answer to my problem, which is...
When I present a simple UIAlertController with a UIAlertAction handler, I am expecting the alert to display until the user responds, then the handler is executed, before continuing with the remaining code.
Unexpectedly, it seems to finish off the code block before displaying the alert and executing the handler.
I've searched Stackoverflow, and re-read the Apple Developer Documentation for UIAlertController and UIAlertAction, but I can't figure out why the code doesn't pause until the user responds.
I've tried putting the UIAlertController code in its own function, but the alert still appears to be displaying out of sequence. I'm thinking maybe there needs to be a delay to allow the Alert to draw before the next line of code executes(?).
#IBAction func buttonTapped(_ sender: Any) {
let alert = UIAlertController(title: "Ouch", message: "You didn't have to press me so hard!", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Sorry", style: .default, handler: { _ in
self.handleAlert()
}))
self.present(alert, animated: true, completion: nil)
print("Should be printed last!")
}
func handleAlert() {
print("UIAlertAction handler printed me")
}
In the code above I am expecting the debug console to display:
UIAlertAction handler printed me
Should be printed last!
But instead it displays:
Should be printed last!
UIAlertAction handler printed me

Answer 1

Instead of adding a seperate function, can you put it within the alert action itself like this...
let alert = UIAlertController(title: "Ouch", message: "You didn't have to press me so hard!", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Sorry", style: .default, handler: { action in
// code for action goes here
}))
self.present(alert, animated: true)

Answer 2

UIAlertController is designed to run asynchronously (that is why it has you pass a block of code to execute when the action is performed instead of giving a return value)
So to fix your code, put the code you want to run after an action is chosen in another function, then call that function at the end of each UIAlertAction handler.
private var currentlyShowingAlert = false
#IBAction func buttonTapped(_ sender: Any) {
if currentlyShowingAlert {
return
}
let alert = UIAlertController(title: "Ouch", message: "You didn't have to press me so hard!", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Sorry", style: .default, handler: { _ in
self.handleAlert()
self.alertCleanup()
}))
self.present(alert, animated: true, completion: nil)
currentlyShowingAlert = true
}
func handleAlert() {
print("UIAlertAction handler printed me")
}
func alertCleanup() {
print("Should be printed last!")
currentlyShowingAlert = false
}
Be careful when doing things like pushing view controllers (or anything where the calls will stack up) in direct response to a button press.
When the main thread is busy, the button can be pressed multiple times before the first buttonTapped call happens, in that case buttonTapped could be called many times in a row, currentlyShowingAlert will prevent that issue.