A little stopwatch

ContentView.swift

class Stopwatch: ObservableObject {
    @Published private var progressTime = 58
    
    var hours: String {
        let time = progressTime / 3600
        return time < 10 ? "0\(time)" : "\(time)"
    }
    
    var minutes: String {
        let time = (progressTime % 3600) / 60
        return time < 10 ? "0\(time)" : "\(time)"
    }
    
    var seconds: String {
        let time = progressTime % 60
        return time < 10 ? "0\(time)" : "\(time)"
    }
    
    var elapsedTime: String {
        hours + ":" + minutes + ":" + seconds
    }
    
    private var timer: Timer?
    
    func start() {
        timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { _ in
            self.progressTime += 1
        })
    }
    
    func stop() {
        timer?.invalidate()
    }
}

struct ContentView: View {
    @ObservedObject var stopwatch: Stopwatch = Stopwatch()
    
    var body: some View {
        VStack {
            Text(stopwatch.elapsedTime)
                .padding()
        }.onAppear() {
            stopwatch.start()
        }
    }
}