Hide/show parent navigation bar

NavigationView2Demo.swift

import SwiftUI

struct NavigationView2Demo: View {
    @State var hide = false

    var body: some View {
        NavigationView {
            NavigationView2Demo_A
            .navigationBarHidden(hide)
            .onAppear { self.hide = true }
        }
    }
    var NavigationView2Demo_A: some View {
        VStack(spacing: 20) {
            NavigationLink(destination: NavigationView2Demo_B) {
                Text("Go to screen B")
            }
            .navigationBarTitle("A")
            Text("Navigation bar should be hidden")
        }
    }

    var NavigationView2Demo_B: some View {
        Text("Navigation bar should not be hidden")
            .navigationBarTitle("B")
            .onAppear { self.hide = false }
    }
}

struct NavigationView2Demo_Previews: PreviewProvider {
    static var previews: some View {
        NavigationView2Demo()
    }
}