use timer to countdown from what is placed in the uitextfield - swift

Question

My swift code below should take whatever number is placed in the textfield and then count it down in by a single second. I dont know how to take what is in the textfield and get it to be counted down from. Dont worry about making sure the user places a number and not a string in the textfield.
import UIKit
class ViewController: UIViewController {
var enterTime = UITextField()
var lblTime = UILabel()
var startBTN = UIButton()
var timer = Timer()
var counter = 33
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
[enterTime,lblTime,startBTN].forEach{
$0.backgroundColor = .systemRed
view.addSubview($0)
$0.translatesAutoresizingMaskIntoConstraints = false
}
enterTime.frame = CGRect(x: view.center.x-115, y: view.center.y-200, width: 60, height: 50)
lblTime.frame = CGRect(x: view.center.x-115, y: view.center.y, width: 60, height: 50)
startBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+200, width: 60, height: 50)
startBTN.addTarget(self, action: #selector(startHit), for: .touchDown)
}
#objc func startHit() {
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
}
#objc func timerAction() {
//This is where the user would take the time from uitextfield and causes it to count down
enterTime.text = counter
lblTime.text = "\(counter)"
}
}

Answer 1

1 ) Invalidate your timer and initiate counter with a value from enterTime textField and start your timer in startHit function.
2 ) In the timerAction function, reduce the counter value by 1 and set it in the lblTime.
You may need to modify your startHit and timerAction functions as follows.
#objc func startHit() {
timer.invalidate()
if let counterText = enterTime.text, let counterValue = Int(counterText) {
counter = counterValue
lblTime.text = String(counter)
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
}
}
#objc func timerAction() {
counter -= 1
lblTime.text = String(counter)
if ( counter == 0 ) {
timer.invalidate()
}
}