How can I output UIAlertController to a separate file and output data from there?

Question

I'm trying to output alert to a separate function, since there will be many similar ones.

Here is my alert:

extension UIViewController {
    func alertEditSum(nameCell: String, completion: (() -> Void)) {
        let alertController = UIAlertController(title: "Hello", message: "", preferredStyle: .alert)
        
        
        alertController.addAction(UIAlertAction(title: "Save", style: .default , handler: { _ in
            let nameFolderField = alertController.textFields![0] as UITextField
            if nameFolderField.isTextFieldCheck(text: nameFolderField.text!) == true {
                
                // -----here----
                
            }
        }))
        
        alertController.addAction(UIAlertAction(title: "Cancel"
                                                
                                                , style: .cancel, handler: nil))
        
        alertController.addTextField(configurationHandler: { (nameField: UITextField!) -> Void in
            nameField.clearButtonMode = .always
            nameField.keyboardType = .decimalPad
            
        })
        
        self.present(alertController, animated: true)
        
    }
    
}

and my piece of code is in another VC:

self.sortedDate[indexPath.section-1].personPayment = Double(nameFolderField.text!)!
 do {
try! self.context.save()
collectionView.reloadData()
}

The problem is that I need to consider what exactly the user enters in UITextField. text! (nameFolderField.text!). I also can't add completion to the alert code, writes an error.

Completion should be added to the line where it says: / / - - - - - here----

Please tell me how to solve this problem?

Answer 1

This should do the trick:

func alertEditSum(nameCell: String, completion: @escaping ((String?) -> Void)) {

    let alertController = UIAlertController(title: "Hello", message: "", preferredStyle: .alert)

    alertController.addAction(UIAlertAction(title: "Save", style: .default, handler: { _ in
        let nameFolderField = alertController.textFields![0] as UITextField
        if nameFolderField.isTextFieldCheck(text: nameFolderField.text!) == true {
            completion(nameFolderField.text)
        }
    }))

    alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { _ in
        completion(nil)
    }))

    alertController.addTextField(configurationHandler: { nameField in
        nameField.clearButtonMode = .always
        nameField.keyboardType = .decimalPad
    })

    self.present(alertController, animated: true)
}

To call it:

theViewController.alertEditSum(nameCell: "text") { text in
    if let text = text {
        //Do stuff
    } else { //Text is invalid or user has cancel

    }
}

Now, isTextFieldCheck(text:) is I guess a method on UITextField, since it's checking its own text, why giving it as a parameter?
Why not just func isTextValid()?

I would also avoid the force unwrap: !.

Going further, would be to use Result<String, Error> in the completion: completion((Result<String, Error>) -> Void)) to have more infos if needed (user has canceled, text wasn't not valid for any reason, etc.)