SwiftUI - How to close the sheet view, while dismissing that view

UPDATE: Restored original version - provided below changes should be done, as intended, to the topic starter's code. Tested as worked with Xcode 13 / iOS 15

As navigation in sheet might be long enough and closing can be not in all navigation subviews, I prefer to use environment to have ability to specify closing feature only in needed places instead of passing binding via all navigation stack.

Here is possible approach (tested with Xcode 11.2 / iOS 13.2)

1. Define environment key to store sheet state

struct ShowingSheetKey: EnvironmentKey {
    static let defaultValue: Binding<Bool>? = nil
}

extension EnvironmentValues {
    var showingSheet: Binding<Bool>? {
        get { self[ShowingSheetKey.self] }
        set { self[ShowingSheetKey.self] = newValue }
    }
}

2. Set this environment value to root of sheet content, so it will be available in any subview when declared

}.sheet(isPresented: $isShowSheet) {
    NavView()
       .environment(\.showingSheet, self.$isShowSheet)
}

3. Declare & use environment value only in subview where it is going to be used

struct NavSubView: View {
    @Environment(\.showingSheet) var showingSheet

    var body: some View {
        Text("Hello")
        .navigationBarItems(trailing:
            Button("Done") {
                self.showingSheet?.wrappedValue = false
            }
        )
    }
}

I haven't tried SwiftUI ever, but I came from UIKit + RxSwift, so I kinda know how binding works. I read quite a bit of sample codes from a SwiftUI Tutorial, and the way you dismiss a modal is actually correct, but apparently not for a navigation stack.

One way I learned just now is use a @Binding var. This might not be the best solution, but it worked!

So you have this $isShowSheet in your ContentView. Pass that object to your NavView struct by declaring a variable in that NavView.

ContentView

    .....

    }.sheet(isPresented: $isShowSheet) {
        NavView(isShowSheet: self.$isShowSheet)
    }

NavView

struct NavView: View {
    @Binding var isShowSheet: Bool

    var body: some View {
        NavigationView {
            NavigationLink(destination: NavSubView(isShowSheet: self.$isShowSheet)) {
                Text("Enter Sub View")
            }
        } .navigationViewStyle(StackNavigationViewStyle())
    }
}

and finally, do the same thing to your subView.

NavSubView

struct NavSubView: View {
    @Environment(\.presentationMode) var presentationMode

    @Binding var isShowSheet: Bool

    var body: some View {
        Text("Hello")
        .navigationBarItems(trailing:
            Button(action: {
                //self.presentationMode.projectedValue.wrappedValue.dismiss()
                self.isShowSheet = false
            }){
                Text("Done")
            }
        )
    }
}

Now as you can see, you just need to send a new signal to that isShowSheet binding var - false.

self.isShowSheet = false

Voila!