Format Number in a Label

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var resultLabel: UILabel!

    var userIsInTheMiddleOfTyping : Bool = false
    
    var usingDecimal = false
    
    var firstNumber : Double = 0.0
    var secondNumber : Double = 0.0
    var result : Float = 0.0
    var choosingOperator : String = ""
    let π = 3.14159265359
    
   
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }


    @IBAction func clearButtonTapped(_ sender: UIButton) {
    
        //resultLabel.text = "C"
        
        firstNumber = 0.0
        secondNumber = 0.0
        result = 0.0
        choosingOperator = ""
        resultLabel.text = ""
        usingDecimal = false
    }
    
    
    
    @IBAction func operatorButtonTapped(_ sender: UIButton) {
        
        // +,-,/,*
       
        if resultLabel.text != "." {
            
            
            firstNumber = Double(resultLabel.text!)!
            
            print(firstNumber)
            
            userIsInTheMiddleOfTyping = false
    
            choosingOperator = sender.currentTitle!
            usingDecimal = false
        }
        
    }
    
    // other operators 
    
    @IBAction func cubicOrQuadraticButtonTapped(_ sender: UIButton) {
        
        firstNumber = Double(resultLabel.text!)!
        choosingOperator = sender.currentTitle!
        
        switch choosingOperator {
        
            case "x²": result = Float(firstNumber * firstNumber)
            case "√": result = Float(sqrt(firstNumber))
            case "x³": result = Float(firstNumber * firstNumber * firstNumber)
            case "∛": result = Float(cbrt(firstNumber))
            
        default: break
        }
        
        resultLabel.text = String(result)
        userIsInTheMiddleOfTyping = false
        usingDecimal = false
        
        
    }
    
    @IBAction func trigButtonTapped(_ sender: UIButton) {
        
        firstNumber = Double(resultLabel.text!)!
        choosingOperator = sender.currentTitle!
        
        switch choosingOperator {
            
        case "sin⁻¹": result = Float(asin(firstNumber) * 180/π)
        case "cos⁻¹": result = Float(acos(firstNumber) * 180/π)
        case "tan⁻¹": result = Float(atan(firstNumber) * 180/π)
            
        default: break
        }
        
        resultLabel.text = String(result)
        userIsInTheMiddleOfTyping = false
        usingDecimal = false
        
    }
    
    
    
    // Number Tapped
    
    @IBAction func keypadButtonTapped(_ sender: UIButton) {
        // resultLabel.text = "Keypad tapped"
        var key = sender.currentTitle!
        print(key)
        if userIsInTheMiddleOfTyping == true {
            if usingDecimal == true && key == "."{
                key = ""
            }
            resultLabel.text = resultLabel.text! + key
        } else {
            resultLabel.text = key
            userIsInTheMiddleOfTyping = true
        }
        if key == "." {
            usingDecimal = true
        }
    }
    // Equals tapped
    @IBAction func equalsButtonTapped(_ sender: UIButton) {
       // resultLabel.text = "Equals Tapped"
        
        secondNumber = Double(resultLabel.text!)!
        
        calculate(_operator: choosingOperator)
        
        resultLabel.text = String(result)

        userIsInTheMiddleOfTyping = false
        usingDecimal = false
     
    }
    
    
    func calculate(_operator: String) {
        
        switch _operator {
            case "": result = Float(firstNumber + secondNumber)
            case "": result = Float(firstNumber - secondNumber)
            case "": result = Float(firstNumber * secondNumber)
            case "": result = Float(firstNumber / secondNumber)
           
            default: break
        }
    }
    
    
}

Hello Apple community!

I am programming a calculator app and I would like to use the NumberFormatter to change the format of larger numbers in my results label.

For example:

345906483

would than be

345'906'483

I have attempted to translate the number using the Number Formatter, which worked

let numberFormatter = NumberFormatter()
numberFormatter.numberStyle = .decimal
numberFormatter.groupingSeparator = "'"
let formattedNumber = numberFormatter.string(from: NSNumber(value: result))
print(formattedNumber!)

resultLabel.text = formattedNumber
userIsInTheMiddleOfTyping = false
usingDecimal = false

However, when I attempt to do further calculations, I have an issue:

The number that stands in my label is now a string with numbers and " ' ", my new calculation doesn't work

I then reversed this formatting at the beginning of each calculation, and then again at the end of calculation:

let numberFormatterReverse = NumberFormatter()
numberFormatterReverse.numberStyle = .none
numberFormatterReverse.usesGroupingSeparator = false
let formattedNumberReverse = numberFormatterReverse.string(from: NSNumber(value: result))
print(formattedNumberReverse!)

resultLabel.text = formattedNumberReverse
firstNumber = Double(resultLabel.text!)!

result = Float(sqrt(firstNumber))

let numberFormatter = NumberFormatter()
numberFormatter.numberStyle = .decimal
numberFormatter.groupingSeparator = "'"
let formattedNumber = numberFormatter.string(from: NSNumber(value: result))
print(formattedNumber!)

resultLabel.text = formattedNumber
userIsInTheMiddleOfTyping = false
usingDecimal = false

I am sure that this is too complicated and I would appreciate some assistance!

Thanks in advance :-)