SwiftUI - prevent auto dismiss the sheet by drag down

gistfile1.txt

//
//  Created by https://quickplan.app on 2020/11/8.
//

import SwiftUI

/// Control if allow to dismiss the sheet by the user actions
/// - Drag down on the sheet on iPhone and iPad
/// - Tap outside the sheet on iPad
/// No impact to dismiss programatically (by calling "presentationMode.wrappedValue.dismiss()")
/// -----------------
/// Tested on iOS 14.2 with Xcode 12.2 RC
/// This solution may NOT work in the furture.
/// -----------------
struct MbModalHackView: UIViewControllerRepresentable {
    var dismissable: () -> Bool = { false }
    
    func makeUIViewController(context: UIViewControllerRepresentableContext<MbModalHackView>) -> UIViewController {
        MbModalViewController(dismissable: self.dismissable)
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        
    }
}

extension MbModalHackView {
    private final class MbModalViewController: UIViewController, UIAdaptivePresentationControllerDelegate {
        let dismissable: () -> Bool
        
        init(dismissable: @escaping () -> Bool) {
            self.dismissable = dismissable
            super.init(nibName: nil, bundle: nil)
        }
        
        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        override func didMove(toParent parent: UIViewController?) {
            super.didMove(toParent: parent)
            
            setup()
        }
        
        func presentationControllerShouldDismiss(_ presentationController: UIPresentationController) -> Bool {
            dismissable()
        }
        
        // set delegate to the presentation of the root parent
        private func setup() {
            guard let rootPresentationViewController = self.rootParent.presentationController, rootPresentationViewController.delegate == nil else { return }
            rootPresentationViewController.delegate = self
        }
    }
}

extension UIViewController {
    fileprivate var rootParent: UIViewController {
        if let parent = self.parent {
            return parent.rootParent
        }
        else {
            return self
        }
    }
}

/// make the call the SwiftUI style:
/// view.allowAutDismiss(...)
extension View {
    /// Control if allow to dismiss the sheet by the user actions
    public func allowAutoDismiss(_ dismissable: @escaping () -> Bool) -> some View {
        self
            .background(MbModalHackView(dismissable: dismissable))
    }
    
    /// Control if allow to dismiss the sheet by the user actions
    public func allowAutoDismiss(_ dismissable: Bool) -> some View {
        self
            .background(MbModalHackView(dismissable: { dismissable }))
    }
}

/// Example:
struct ContentView: View {
    @State private var presenting = false
    
    var body: some View {
        VStack {
            Button {
                presenting = true
            } label: {
                Text("Present")
            }
        }
        .sheet(isPresented: $presenting) {
            ModalContent()
                .allowAutoDismiss { false }
                // or
                // .allowAutoDismiss(false)
        }
    }
}
struct ModalContent: View {
    @Environment(\.presentationMode) private var presentationMode
    
    var body: some View {
        VStack {
            Text("Hello")
                .padding()
            
            Button {
                presentationMode.wrappedValue.dismiss()
            } label: {
                Text("Dismiss")
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Thanks @mobilinked, you're a lifesaver.

Thanks !

Brilliant solution! Thanks so much!

Thank you!