Instance method 'onReceive(_:perform:)' requires that 'CountdownTimer' conform to 'Publisher'

I’m currently building out a project where a user could create multiple timers however I’m running into the following error. "Instance method ‘onReceive(_:perform:)’ requires that ‘CountdownTimer’ conform to ‘Publisher’". I just can’t figure out how to get Countdown Timer to conform to Publisher.

Here is the code for my timer object:

struct CountdownTimer: Identifiable {
  let id = UUID()
  let name: String
  var minutes: Int
  var seconds: Int

  var countdown: Int  {
    let totalTime = seconds + (minutes * 60)
        return totalTime
  }
} 

func timeString(time: Int) -> String {
    return String(format: "%01i:%02i", minutes, seconds)

}
  

class CountdownTimers: ObservableObject {
  @Published var timers = [CountdownTimer]()
}

My Content View:

struct ContentView: View {
@Environment(\.presentationMode) var presentationMode
@ObservedObject var countdownTimers = CountdownTimers()

@State private var showingAddSheet = false


let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()

var body: some View {
    NavigationView {
        GeometryReader { geometry in
            ZStack {
                Color.pastelGreen
                    .edgesIgnoringSafeArea(.all)
                VStack {
                    ScrollView {
                        ForEach(countdownTimers.timers) { timer in
                            ZStack {
                                CardView()
                                    .overlay(
                                        HStack {
                                            VStack(alignment: .leading) {
                                                Text("\(timer.countdown)")
                                                    .font(.custom("Quicksand-Bold", size: 30))
                                                Text(" \(timer.timeString(time: timer.countdown))")
                                                    .font(.custom("Quicksand-Bold", size: 40))
                                                    .onReceive(timer){ _ in
                                                        if timers.countdown > 0 {
                                                            timers.countdown -= 1
                                                        }
                                                    }

The error is happening on the .OnReceive(timer) line. the minutes and seconds are created on a different "AddView" but I don’t believe that the issue is related to that section.

Any help would be greatly appreciated.

>Solution :

You’re shadowing the name timer. It appears first here:

let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()

Then, later, you use it again here:

ForEach(countdownTimers.timers) { timer in

Swift is going to assume you always mean the timer in the most-recently-defined scope, so when you use .onReceive, it assumes you mean timer from the ForEach (which is of type CountdownTimer) and not the Timer defined earlier.

To fix this, use a different name in your ForEach and adjust your code (such as the Text elements) to use the new name.