SwiftUI pulse animation

Pulse.swift

struct ContentView: View {
    static let fadeInDuration = CGFloat(1.1)
    static let pulseDuration = CGFloat(1.6)
    static let fadeOutDuration = CGFloat(0.3)
    static let interval = CGFloat(1.6)

    @State var isAnimating = false
    @State var timer = Timer.publish(every: interval, on: .main, in: .common).autoconnect()
    @State var circlesIDs = [UUID()]

    var body: some View {
        Color.gray.overlay {
            ZStack {
                ForEach(circlesIDs, id: \.self) { _ in
                    circle
                }
            }
        }
        .onReceive(timer) { _ in
            if isAnimating {
                circlesIDs.append(UUID())
                circlesIDs.removeFirst()
            }
        }
        .onTapGesture {
            isAnimating.toggle()
        }
    }

    var circle: some View {
        Circle()
            .frame(width: 30)
            .foregroundColor(.yellow)
            .transition(
                .asymmetric(
                    insertion: .pulse /// Special transition that starts out with 1 opacity and goes to 0.
                        .animation(
                            .easeInOut(duration: Self.pulseDuration)
                        )
                        .combined(with: /// Add the fade in transition.
                            .opacity
                                .animation(
                                    .linear(duration: Self.fadeInDuration)
                                )
                        ),
                    removal: .opacity /// For removal, a simple opacity fade is fine.
                        .animation(
                            .easeInOut(duration: Self.fadeOutDuration)
                        )
                )
            )
    }
}

extension AnyTransition {
    static var pulse: AnyTransition {
        .modifier(
            active: PulseModifier(transitioning: true),
            identity: PulseModifier(transitioning: false)
        )
    }
}

struct PulseModifier: ViewModifier {
    var transitioning: Bool

    func body(content: Content) -> some View {
        content
            .opacity(transitioning ? 1 : 0)
            .scaleEffect(transitioning ? 0.45 : 2)
    }
}

Result:

PulseAnimation.mov