Stop Watch

contentView(complete).swift

import SwiftUI

struct ContentView: View {
    
    @ObservedObject var stopWatchManeger = StopWatchManeger()
    
    var body: some View {
        VStack {
            Text(String(format:"%.1f",stopWatchManeger.secondsElapsed))
                .font(.custom("Futura", size: 50))
                .padding(.top,200)
                .padding(.bottom,100)
                .padding(.trailing,100)
                .padding(.leading,100)
            
            if stopWatchManeger.mode == .stop{
                Button(action: {self.stopWatchManeger.start()}){
                             ExtractedView(label: "Start", buttonColor: .yellow, textColor: .black)
                }
            }
            
            if stopWatchManeger.mode == .start{
                Button(action: {self.stopWatchManeger.pause()}){
                ExtractedView(label: "Pause", buttonColor: .yellow, textColor: .black)
                }
                
            }
                
            if stopWatchManeger.mode == .pause{
                Button(action: {self.stopWatchManeger.start()}){
                ExtractedView(label: "Start", buttonColor: .yellow, textColor: .black)
                       }
                Button(action: {self.stopWatchManeger.stop()}){
                ExtractedView(label: "Stop", buttonColor: .red, textColor: .black)
                       }
                .padding(.top,10)
            
            }
            Spacer()
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

struct ExtractedView: View {
    var label:String
    var buttonColor:Color
    var textColor:Color
    
    var body: some View {
        Text(label)
            .foregroundColor(textColor)
            .padding(.vertical,20)
            .padding(.horizontal,90)
            .background(buttonColor)
            .cornerRadius(10)
    }
}

StopWatchmaneger(complete).swift

class StopWatchManeger:ObservableObject{
    
    enum stopWatchMode{
        case start
        case stop
        case pause
    }
    
    @Published var mode:stopWatchMode = .stop
    
    @Published var secondsElapsed = 0.0
    var timer = Timer()
    
    func start(){
        mode = .start
        timer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true){ timer in
            self.secondsElapsed += 0.1
        }
    }
    
    func stop(){
        timer.invalidate()
        secondsElapsed = 0
        mode = .stop
    }
    
    func pause(){
         timer.invalidate()
        mode = .pause
     }
}