Is it possible to make a modal non-dismissible in SwiftUI?

Question

I am creating an App where the login / register part is inside a modal, which is shown if the user is not logged in.

The problem is, that the user can dismiss the modal by swiping it down...

Is it possible to prevent this?

var body: some View {
    TabView(selection: $selection) {
        App()
    }.sheet(isPresented: self.$showSheet) { // This needs to be non-dismissible
        LoginRegister()
    }
}

Second example:

I am using a modal to ask for information. The user should not be able to quit this process except by dismissing the modal with save button. The user has to input information before the button works. Unfortunately the modal can be dismissed by swiping it down.

Is it possible to prevent this?

Answer 1

iOS 15 and later:

Use .interactiveDismissDisabled(true) on the sheet, that's all.

Prev iOS 15:

You can try to do this by using a highPriorityGesture. Of course the blue Rectangle is only for demonstration but you would have to use a view which is covering the whole screen.

struct ModalViewNoClose : View {
    @Environment(\.presentationMode) var presentationMode
    
    let gesture = DragGesture()
    
    var body: some View {
        
        Rectangle()
            .fill(Color.blue)
            .frame(width: 300, height: 600)
            .highPriorityGesture(gesture)
            
            .overlay(
                VStack{
                    Button("Close") {
                        self.presentationMode.value.dismiss()
                    }.accentColor(.white)
                    Text("Modal")
                        .highPriorityGesture(gesture)
                    TextField("as", text: .constant("sdf"))
                        .highPriorityGesture(gesture)
                } .highPriorityGesture(gesture)
        )
            .border(Color.green)
    }
}