SwiftUI：如何弹出到根视图

最后，在Beta 5中，我们可以通过编程方式弹出到父视图.然而，在我的应用程序中，有几个地方的视图有一个"保存"按钮，可以结束一个多步骤的过程并返回到开始.在UIKit中，我使用popToRootViewController()，但我一直无法找到在SwiftUI中执行同样操作的方法.

下面是我试图实现的模式的一个简单示例.有什么 idea 吗？

import SwiftUI

struct DetailViewB: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        VStack {
            Text("This is Detail View B.")

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop to Detail View A.") }

            Button(action: { /* How to do equivalent to popToRootViewController() here?? */ } )
            { Text("Pop two levels to Master View.") }

        }
    }
}

struct DetailViewA: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        VStack {
            Text("This is Detail View A.")

            NavigationLink(destination: DetailViewB() )
            { Text("Push to Detail View B.") }

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop one level to Master.") }
        }
    }
}

struct MasterView: View {
    var body: some View {
        VStack {
            Text("This is Master View.")

            NavigationLink(destination: DetailViewA() )
            { Text("Push to Detail View A.") }
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            MasterView()
        }
    }
}