Long delay when presenting UIAlert - swift

Question

I'm having a problem with presenting an alert. I'm using UIAlertController. When the user presses the submit button, an alert needs to be presented immediately saying "Please Wait.." while the app does some operations. The alert is dismissed after the operations are complete. I'm having a long delay (several seconds) before the alert is presented even though the alert is supposed to be presented before i even start doing the operations. I tried dispatch async and tried using closures and nothing is working..still a delay of several seconds before alert is presented.
How do i make it so that the alert is presented immediately after the button the pressed?
override func viewDidLoad() {
super.viewDidLoad()
submitButton.addTarget(self,action:#selector(buttonAction),for:.touchUpInside)
}
#objc func buttonAction(){
waiting()
doOperations()
}
func waiting(){
DispatchQueue.main.async{
let alert = UIAlertController(title: nil, message: "Please wait...", preferredStyle: .alert)
let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
loadingIndicator.hidesWhenStopped = true
loadingIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray
loadingIndicator.startAnimating()
alert.view.addSubview(loadingIndicator)
self.present(alert, animated: false, completion: nil)
}
}
func doOperations(){
...
}
func dismissWaiting{
...
//dismiss alert
}

Answer 1

Just dispatch to main thread the alert.

Answer 2

Hey I resolved the problem just by putting the call to doOperations in the completion of the presentation of the alert. Like this:
self.present(alert, animated: false, completion: {self.doOperations()})
Now the alert is presented instantly after button press and everything works fine. Thanks guys for all the suggestions.