Problems Updating View with Swift 5 - ios

Question

I am having some trouble updating my secondViewController view in Xcode using Swift 5. I want my app to add two numbers together and show the result in the second ViewController. Although it works the first time, if I return to my previous view and change the numbers, the view does not update.
I tried using viewWillAppear, viewWillDisappear, amongst others, including NSNotificationCenter addObserve, but I have had no luck whatsoever.
Do you have any recommendations? Am I missing something?
Please see below for the code and a screenshot of my ViewControllers:
//
// ViewController.swift
//
import UIKit
var result = ""
var resultFinal = Float(result)
let finalResult = resultFinal!
class ViewController: UIViewController {
#IBOutlet weak var firstNumber: UITextField!
#IBOutlet weak var secondNumber: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
func getResult()-> Float{
guard let fNumber = firstNumber.text else {
return 0
}
let firstFloat = Float(fNumber)
guard let sNumber = secondNumber.text else {
return 0
}
let secondFloat = Float(sNumber)
let sumNumber: Float = firstFloat! + secondFloat!
return sumNumber
}
#IBAction func submitSum(_ sender: Any) {
resultFinal = getResult()
print(resultFinal!)
}
}
//
// secondViewController.swift
//
import UIKit
class secondViewController: UIViewController {
#IBOutlet weak var test: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
self.test.text!=""
// Do any additional setup after loading the view.
}
override func viewWillAppear(_ animated: Bool) {
test.text = String(finalResult)
}
}
Screenshot:
Thanks.

Answer 1

Your problem is with the global variables. It seems from your code that you expect these three to reevaluate every time one of them changes:
var result = ""
var resultFinal = Float(result)
let finalResult = resultFinal!
For example, if you set resultFinal = 4, then finalResult will equal 4. However, those variables only evaluate once––the first time. You can simplify your use of these variables significantly. Replace these three with:
var result: Float?
Then, in ViewController:
class ViewController: UIViewController {
#IBOutlet weak var firstNumber: UITextField!
#IBOutlet weak var secondNumber: UITextField!
func getResult() -> Float {
guard let number1 = Float(firstNumber.text ?? "0") ?? 0
guard let number2 = Float(secondNumber.text ?? "0") ?? 0
return number1 + number2
}
#IBAction func submitSum(_ sender: Any) {
result = getResult()
}
}
Note: I simplified getResult and made it treat empty fields as 0.
In SecondViewController:
class SecondViewController: UIViewController {
#IBOutlet weak var test: UITextField!
override func viewWillAppear(_ animated: Bool) {
test.text = String(result ?? 0)
}
}
Note: self.test.text!="" doesn't really do anything, so I removed it.