An approach to use SwiftUI views inside UIKit Coordinator

UIKit-SwiftUI-Coordinator.swift

class Coordinator: UINavigationController {
    init() {
        super.init(nibName: nil, bundle: nil)

        let firstVC = HostingController { FirstView(push: push) }

        setViewControllers([firstVC], animated: false)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func push() {
        let screen = SecondView(navigationPropagation: NavigationPropagation(), present: present)
        let vc = HostingController(navigationPropagation: screen.navigationPropagation) { screen }

        pushViewController(vc, animated: true)
    }

    func present() {
        let vc = HostingController { ThirdView() }

        present(vc, animated: true)
    }
}

class HostingController<Content: View>: UIHostingController<Content> {
    var subscriptions = Set<AnyCancellable>()

    init(navigationPropagation: NavigationPropagation = NavigationPropagation(), @ViewBuilder _ view: () -> Content) {
        super.init(rootView: view())

        navigationPropagation.screenTitleSubject
            .sink { [weak self] screenTitle in
                self?.navigationItem.title = screenTitle
            }
            .store(in: &subscriptions)

        navigationPropagation.leadingNavigationButtonsSubject
            .sink { [weak self] leadingButtons in
                self?.navigationItem.leftBarButtonItems = leadingButtons
            }
            .store(in: &subscriptions)

        navigationPropagation.trailingNavigationButtonsSubject
            .sink { [weak self] trailingButtons in
                self?.navigationItem.rightBarButtonItems = trailingButtons
            }
            .store(in: &subscriptions)
    }

    @MainActor required dynamic init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

struct FirstView: View {
    let push: () -> Void

    var body: some View {
        Button("Push", action: push)
    }
}

struct SecondView: View {
    let navigationPropagation: NavigationPropagation
    let present: () -> Void

    var body: some View {
        VStack {
            Button("Present", action: present)

            Button("Change title") {
                navigationPropagation.screenTitleSubject.send(String("qwertyuiopasdfghjklzxcvbnm".randomElement()!))
            }
        }
    }
}

struct ThirdView: View {
    var body: some View {
        Text("Hello world!")
    }
}

class NavigationPropagation {
    let leadingNavigationButtonsSubject: CurrentValueSubject<[UIBarButtonItem], Never>
    let trailingNavigationButtonsSubject: CurrentValueSubject<[UIBarButtonItem], Never>
    let screenTitleSubject: CurrentValueSubject<String?, Never>

    init(
        screenTitle: String? = nil,
        leadingNavigationButtons: [UIBarButtonItem] = [],
        trailingNavigationButtons: [UIBarButtonItem] = []
    ) {
        self.screenTitleSubject = CurrentValueSubject(screenTitle)
        self.leadingNavigationButtonsSubject = CurrentValueSubject(leadingNavigationButtons)
        self.trailingNavigationButtonsSubject = CurrentValueSubject(trailingNavigationButtons)
    }
}