1.使用Rectangle()绘制

struct ContentView: View {
    var body: some View {
        Rectangle()
            .strokeBorder(style: StrokeStyle(lineWidth: 4, dash: [10]))
    }
}

在dash参数中使用[10]意味着SwiftUI将绘制10个笔划点，然后再绘制10个点的间距 它是一个数组，因为您可以提供多个值，例如[10,5]，表示“10个笔划点，然后是5个点间距

2.给虚线做动画

struct ContentView: View {
    @State private var phase: CGFloat = 0

    var body: some View {
        Rectangle()
            .strokeBorder(style: StrokeStyle(lineWidth: 4, dash: [10], dashPhase: phase))
            .frame(width: 200, height: 200)
            .onAppear {
                withAnimation(.linear.repeatForever(autoreverses: false)) {
                    phase -= 20
                }
            }
    }
}

原文:https://www.hackingwithswift.com/quick-start/swiftui/how-to-create-a-marching-ants-border-effect