[SwiftUI] Simple Countdown

In a workout app, it’s common to display a countdown timer at the start of a workout to prepare the user. Let’s create this countdown using SwiftUI.

Code

Here’s how you can implement the countdown in SwiftUI:

import Combine
import SwiftUI

struct CountDownView: View {
    @State private var timeRemaining = 5
    @State private var scale: CGFloat = 1.0
    @State private var opacity: CGFloat = 0

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

    var body: some View {
        Text("\(timeRemaining)")
            .font(.system(size: 100))
            .scaleEffect(scale)
            .opacity(opacity)
            .onReceive(timer) { _ in
                if timeRemaining > 0 {
                    withAnimation(.bouncy(duration: 0.3)) {
                        scale = 3
                        opacity = 1
                    }
                    DispatchQueue.main.asyncAfter(deadline: .now() + 0.6) {
                        scale = 1
                        opacity = 0.0
                        timeRemaining -= 1
                    }
                    if timeRemaining == 0 {
                        timer.upstream.connect().cancel()
                    }
                }
            }
    }
}

#Preview {
    CountDownView()
}

How It Works

1. Timer Setup:
   I use Timer.publish(every: 1, on: .main, in: .common).autoconnect() to create a timer that fires every second and automatically starts when the view appears.
2. Animation:
   withAnimation(.bouncy(duration: 0.3)) animates the number by increasing its size and making it visible.
   After 0.6 seconds, set the next number.
3. Countdown Logic:
   The timeRemaining variable controls the countdown. When it reaches 0, the timer stops to prevent further updates.

I hope this will be helpful to you!