How can I perform a segue after receive an alert answer - ios

Question

Today I'd like to try to make a part of an application that after show an alert perform a segue ONLY if the user press on the "Yes" alert's button.
To explain me better I'd like that the application will show an aller that say "Are you sure to return to Home?" and it will have two Botton: "Yes" and "No". If the user press no nothing happen, if the user press yes the application perform a segue. The problem is that I don't know how to do it.
I try to write some code line but it doesn't work.
func Alert (TITLE: String, MESSAGE: String) -> Bool()
{
var X = false
let Alert = UIAlertController(title: TITLE, message: MESSAGE, preferredStyle: UIAlertControllerStyle.alert)
Alert.addAction(UIAlertAction(title: "Yes", style: UIAlertActionStyle.default, handler: { (Action) in
X = true
Alert.dismiss(animated: true, completion: nil)
}))
self.present(Alert, animated: true, completion: nil)
Alert.addAction(UIAlertAction(title: "No", style: UIAlertActionStyle.default, handler: nil))
self.present(Alert, animated: true, completion: nil)
return X
}
#IBAction func ButtonAct(_ sender: Any) //This happen if you click the botton on the screen of the iPhone
{
if Alert (TITLE: "Return to Home", MESSAGE: "Are you sure to return Home?")
{performSegue(withIdentifier: "Segue", sender: self)}
}
Thank you for you Help

Answer 1

There are several problems with your code:
No part of your code is calling the #IBAction method, that is why the segue is not being performed. The alert controller only provides you with completion handlers; there is no target/action mechanism like with UIButton.
The boolean return value is determined inside the action's completion handler, asynchronously. Your function returns right away the value false, before the user has had a chance to chose. Things happen in this order:
Call alert()
Function presents UIAlertController
Function returns false
(very many milliseconds pass)
User taps "YES"
Completion handler is executes and x is set to true, but the alert() method has already returned false.
You are presenting the alert twice, once after adding each action. You need to add both actions and then present it only once.
Please use standard capitalization in your code.
Try something like this:
func alert (title: String, message: String, completion: ((Bool) -> Void)) {
let alertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
alertController.addAction(UIAlertAction(title: "Yes", style: .default, handler: { (action) in
alertController.dismiss(animated: true, completion: nil)
completion(true) // true signals "YES"
}))
alertController.addAction(UIAlertAction(title: "No", style: UIAlertActionStyle.default, handler: { (action) in
alertController.dismiss(animated: true, completion: nil)
completion(false) // false singals "NO"
}))
self.present(alertController, animated: true, completion: nil)
}
...and call it like this:
alert(title: "Hi", message: "Want to proceed?", completion: { result in
if result {
self.performSegue(withIdentifier: "Segue", sender: self)
}
})