Update view on a real minute change

Question

I am trying to update view every real minute change. I can't find any Notification publishers that can trigger that, so I have an idea to start timer when next minute changing, but I don't really know how to do it( I've tried this code, not seems to work:

.onChange(of: Calendar.current.component(.minute, from: Date())) { _ in
                print("Minute has Changed")
                
                if calendarViewModel.isTimerAlreadyPublishing {
                    print("Timer continue publishing")
                } else {
                    calendarViewModel.startTimer()
                }
            }

Maybe someone can say more methods how can I accomplish that goal?

Answer 1

You can achieve this with Timer, starting it when actual minute changes in current time zone and updating view every 60 seconds:

struct ContentView: View {
    @State var currentDate = Date()
    @State var timer: Timer?

    var body: some View {
        Text("Current minute: \(currentDate.minute)")
            .onAppear {
                startMinuteTimer()
            }
        
            .onChange(of: currentDate) {_ in
                //this is called when every real minute changes in current TimeZone
            }

    }

    private func startMinuteTimer() {
        // Get the number of seconds to the next minute
        let seconds = 60 - Calendar.current.component(.second, from: .now)
        // Set the initial timer to sync with the next minute change
        DispatchQueue.main.asyncAfter(deadline: .now() + Double(seconds)) {
            self.currentDate = Date()
            // After the first trigger, set a timer to repeat every minute
            self.timer = Timer.scheduledTimer(withTimeInterval: 60, repeats: true) { _ in
                self.currentDate = Date()
            }
        }
    }
}

extension Date {
    var minute: Int {
        return Calendar.current.component(.minute, from: self)
    }
}

#Preview {
    ContentView()
}