Swift UIKit / presenting UIAlert blocks pushing VC - ios

Question

I got simple UIViewController + UIAlert extension:
extension UIViewController {
func alert(title: String = "", message: String){
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: Localized.ok(), style: .default, handler: nil))
present(alert, animated: true, completion: nil)
}
}
Within the ViewController I got a method:
func findUser() {
userService.findUser { (userinfo, error) in
if error != nil {
if let errText = error?.localizedDescription {
self.alert(message: errText)
}
self.doAuth()
return
}
}
}
this doAuth() method should redirect to loginViewController using:
navigationController?.pushViewController(loginViewController, animated: false)
The problem is, that in this scenario, this push doesn't work (nothing appears) (I click OK button on the alert, alert dissapears but loginViewController is not pushed)
I refactored extension a little bit:
extension UIViewController {
func alert(title: String = "", message: String, action completion: (() -> Void)? = nil){
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: Localized.ok(), style: .default, handler: { _ in
completion?()
}))
present(alert, animated: true, completion: nil)
}
}
so findUser() method is calling doAuth() in differently:
func findUser() {
userService.findUser { (userinfo, error) in
if error != nil {
if let errText = error?.localizedDescription {
self.alert(message: errText){ [weak self] in
self?.doAuth()
}
}
return
}
}
}
and it works!
Problem is I have no idea why. And what could have happened in the first scenario?
I feel it should be some simple explanation, but I can't figure it out.
Edit
The explanation is simple and was printed in the console:
pushViewController:animated: called on <UINavigationController 0x7f86050b4400>
while an existing transition or presentation is occurring; the navigation stack
will not be updated.
So doAuth() (with pushing VC method) was called while alert was visible/presented, so alert took the focus and VC couldn't be pushed.
cc: #Paulw11 # cookednick

Answer 1

Problem is navigating and presenting in same if statement
If error != nil , means it only show the alert not try to doAuth().
But you are calling doAuth() in same if block then it is trying to present alert as well as to navigate
func findUser() {
userService.findUser { (userinfo, error) in
if error != nil {
if let errText = error?.localizedDescription {
self.alert(message: errText)
}
return
}
//Out side if block
self.doAuth()
}
}