Fixed plus improved PresentationLink

PresentationLink.swift

// Fixes PresentationLink so that a modal can be opened multiple times.
//
// Also adds .isModalInPresentation(_ value: Bool) modifier to control
// if the modal can be closed or not.
//
// Usage:
//
// In your SceneDelegate.swift:
//
// let presentationHelper = PresentationHelper()
// let viewController = UIHostingController(rootView: ContentView().environmentObject(presentationHelper))
// presentationHelper.viewController = viewController
// window.rootViewController = viewController
//
// After this you can use PresentationLink as normal (as long as this code is part of your module).
//
// You can close the modal using the default swipe gesture or by using the @Environment(\.isPresented)
// binding. For example:
//
// @Environment(\.isPresented) var isPresented
// ...
// Button(action: { isPresented?.value = false }) {
//     Text("Done")
// }
//
// You can also use the PresentationHelper to open modals directly from an action:
//
// @EnvironmentObject presentationHelper: PresentationHelper
// ...
// Button(action: { self.presentationHelper.present(Text("Hello!")) }) {
//     Text("Say Hello!")
// }

import Foundation
import SwiftUI
import Combine

struct ModalContent<Content: View>: View {
    @EnvironmentObject var presentationHelper: PresentationHelper
    
    public let content: Content
    
    var body: some View {
        content
            .environment(\.isPresented, $presentationHelper.isPresented)
    }
}

class PresentationHelper: BindableObject {
    public let didChange = PassthroughSubject<Void, Never>()
    
    public var isPresented: Bool = false {
        didSet {
            if !isPresented && isModalInPresentation {
                isPresented = true
            } else if !isPresented {
                viewController?.dismiss(animated: true)
            }
        }
    }
    
    public var isModalInPresentation: Bool = false {
        didSet {
            viewController?.isModalInPresentation = isModalInPresentation
        }
    }

    public var viewController: UIViewController? {
        didSet {
            didChange.send()
        }
    }
    
    public func present<Destination: View>(_ destination: Destination, onDismiss: (() -> Void)? = nil) {
        let presentationHelper = PresentationHelper()
        let rootView = ModalContent(content: destination).environmentObject(presentationHelper)
        let viewController = UIHostingController(rootView: rootView)
        presentationHelper.viewController = viewController
        self.viewController?.present(viewController, animated: true, completion: onDismiss)        
    }
}

public struct PresentationLink<Label: View, Destination: View>: View {
    @EnvironmentObject private var presentationHelper: PresentationHelper
    public let destination: Destination
    public let label: () -> Label
    
    public init(_ destination: Destination, label: @escaping () -> Label) {
        self.destination = destination
        self.label = label
    }
    
    public var body: some View {
        Button(action: present) {
            label()
        }
    }
    
    private func present() {
        presentationHelper.present(destination)
    }
}

public struct IsModalInPresentationModifier: ViewModifier {
    @EnvironmentObject var presentationHelper: PresentationHelper
    
    private let value: Bool
    
    public init(_ value: Bool) {
        self.value = value
    }
    
    public func body(content: Content) -> some View {
        // dirty way of modifying the isModalInPresentation property, but currently don't know of any other way
        presentationHelper.isModalInPresentation = self.value
        return content.offset(x: 0, y: 0) // need to modify the view else our modifier will not be called
    }
}

public extension View {
    func isModalInPresentation(_ value: Bool) -> Modified<IsModalInPresentationModifier> {
        return modifier(IsModalInPresentationModifier(value))
    }
}

I don't know if I'm doing this wrong but I'm supposed to just add this as a file to my project and then add the stuff into SceneDelegate right? Whenever I do this I just get a lot of errors in both PresentationLink.swift and in my SceneDelegate. Any help with this would be much appreciated.