How can I automatically update TextField in swiftUI - timer

Question

I'm new in swiftUI developing, and I have a little problem. I made a function using Timer to create a count up timer. I want to display the time updating in a TextField, but it doesn't work (with a Text it works). Here is the code:
import SwiftUI
struct ContentView: View {
#State var min: Int = 0
#State var sec: Int = 0
#State var time = ""
#State var timer: Timer? = nil
var body: some View {
NavigationView{
VStack{
TextField("Tempo (min o mm:ss)", text: $time)
HStack{
Button(action: {
self.start()
self.time = String(self.min)+":"+String(self.sec)
}){
Text("Start")
}
Button(action: {
self.stop()
}){
Text("Stop")
}
}
}//VStack
}//NavigationView
}//body
func start(){
timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true){
temp in
self.sec = self.sec + 1
if(self.sec == 59){
self.sec = 0
self.min = self.min + 1
}
}
}
func stop(){
timer?.invalidate()
timer = nil
}
}//contetView

Answer 1

You don't see the change because you're not updating the time String in your timer loop.
Here's the fix:
func updateTimeString() {
self.time = String(format: "%02d:%02d", self.min, self.sec)
}
func start(){
timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { temp in
self.sec = self.sec + 1
if self.sec == 59 {
self.sec = 0
self.min = self.min + 1
}
updateTimeString()
}
}
Notes:
I moved the code to set the time string to a separate function. You can then call this from your Button as well.
I used String(format:) to add formatting to your string to show 2 digits for the minutes and seconds.