Code works on iOS simulator (iPhone 13mini) chrashes on real iPhone 13mini: Fatal error: Unexpectedly found nil while unwrapping an Optional value

Question

Can anyone help: The code works on iOS simulator (iPhone 13mini) chrashes on real iPhone 13mini: Fatal error: Unexpectedly found nil while unwrapping an Optional value.

I don't understand how "bill" can be nil since it was checked before actually unwrapping it.

enter image description here

import UIKit

class CalculatorViewController: UIViewController {

    @IBOutlet weak var billTextField: UITextField!
    @IBOutlet weak var zeroPctButton: UIButton!
    @IBOutlet weak var tenPctButton: UIButton!
    @IBOutlet weak var twentyPctButton: UIButton!
    @IBOutlet weak var splitNumberLabel: UILabel!
    
    var tip = 0.10
    var numberOfPeople = 2
    var billTotal = 0.0
    var finalResult = "0.0"
    
    @IBAction func tipChanged(_ sender: UIButton) {
        
        billTextField.endEditing(true)
        
        zeroPctButton.isSelected = false
        tenPctButton.isSelected = false
        twentyPctButton.isSelected = false
        sender.isSelected = true
        
        let buttonTitle = sender.currentTitle!
        let buttonTitleMinusPercentSign =  String(buttonTitle.dropLast())
        let buttonTitleAsANumber = Double(buttonTitleMinusPercentSign)!
        tip = buttonTitleAsANumber / 100

    }
    
    @IBAction func stepperValueChanged(_ sender: UIStepper) {
        splitNumberLabel.text = String(format: "%.0f", sender.value)
        numberOfPeople = Int(sender.value)
    }
    
    @IBAction func calculatePressed(_ sender: UIButton) {
        
        let bill = billTextField.text!
        if bill != "" {
            billTotal = Double(bill)!
            let result = billTotal * (1 + tip) / Double(numberOfPeople)
            finalResult = String(format: "%.2f", result)
        }
        self.performSegue(withIdentifier: "goToResults", sender: self)
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        
        if segue.identifier == "goToResults" {
            
            let destinationVC = segue.destination as! ResultsViewController
            destinationVC.result = finalResult
            destinationVC.tip = Int(tip * 100)
            destinationVC.split = numberOfPeople
        }
    }
}

Answer 1

Thank you very much. I finally found the solution myself: The problem was that I was using an iPhone localized in Germany. Therefore the input string didn't have a dot but a comma as seperator (25.50 vs 25,50).

So, I replaced the line let bill = billTextField.text! with let bill = (billTextField.text?.replacingOccurrences(of: ",", with: "."))! and it now works well. :-)