how can I add a addition feature into my Xcode project - ios

Question

I have a textfield in my firstViewContoller and thats where the user types in some numbers. Then in my secondViewController i have a label and in that label I want the number entered by the user to be shown. I have done till this but I dont know how I can take the value the user enters in the textfield every time and add it all up and show the result in the label. For example the user enters 5 so now the label is showing 5 then the user types in 20 and now i want the label to add that up and show 25 and keep on adding what the user enters.
// ViewController.swift
import UIKit
class ViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var amountSpent: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
amountSpent.delegate = self
amountSpent.keyboardType = .numberPad }
private func amountSpent(_ amountSpent: UITextField,
shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let invalidCharacters = CharacterSet(charactersIn: "0123456789").inverted
return string.rangeOfCharacter(from: invalidCharacters) == nil }
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let resultViewController = segue.destination as! ResultViewController
resultViewController.recievedInt = amountSpent.text!
}
#IBAction func buttonPressed(_ sender: Any) {
self.performSegue(withIdentifier: "goToResult", sender: nil) } }
// ResultViewController.swift
import UIKit
class ResultViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var totalAmount: UILabel!
var recievedInt = ""
override func viewDidLoad() {
super.viewDidLoad()
totalAmount.text = recievedInt
}
}

Answer 1

Convert the new and the existing values from string to Int and add them together before setting the label to the new total
class ResultViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var totalAmount: UILabel!
var recievedInt = ""
override func viewDidLoad() {
super.viewDidLoad()
if let newValue = Int(recievedInt), let total = Int(totalAmount.text!) {
let newTotal = newValue + total
totalAmount.text = "\(newTotal)"
}
}
An alternative way to do it could be
override func viewDidLoad() {
super.viewDidLoad()
let newValue = Int(recievedInt) ?? 0
let total = Int(totalAmount.text!) ?? 0
let newTotal = newValue + total
totalAmount.text = "\(newTotal)"
}

Answer 2

Create a string variable to store the total value
var totalValue = "0"
Add the below method to your project. This will add all your entered values and will return the total value as a string.
private func getTotalCount(string: String) -> String {
let strTotal = "\(totalCount) + \(string)"
let arithmeticExpression = NSExpression(format: strTotal)
let additionResult = arithmeticExpression.expressionValue(with: nil, context: nil) as! Int
return String(additionResult)
}
You will click the done/return button after you entered the count in the text field, the delegate method will be triggered. Call the getTotalCount() method inside the delegate method as below:
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
totalCount = self.getTotalCount(string: textField.text ?? "0")
textField.resignFirstResponder()
return true
}
Thus adding new counts will be automatically handled inside the UITextField delegate method. You just need to pass the totalValue to the next View Controller like this:
let resultViewController = segue.destination as! ResultViewController
resultViewController.recievedInt = totalCount