lammertw

struct CountView: UIViewControllerRepresentable {

    @EnvironmentObject var counter: ObservableCounter

    typealias UIViewControllerType = CountViewController

    func makeUIViewController(context: Context) -> CountViewController {
        return CountViewController()
    }

lammertw

class CountViewController: UIViewController {

    private let countLabel = UILabel()

    var count = 0 {
        didSet {
            countLabel.text = "Current count: \(count)"
        }
    }

lammertw

struct ContentView: View {

    @EnvironmentObject var counter: ObservableCounter

    var body: some View {
        VStack {
            Text("Current count: \(counter.count)")
            Button("Increment", action: { counter.increment() })
        }
            .padding()

lammertw

class ObservableCounter: ObservableObject {
    @Published var count = 0

    func increment() {
        count += 1
    }
}

@main
struct MyApp: App {

lammertw

struct RestaurantDetailView: View {

    let viewModel: RestaurantDetailViewModel

    var body: some View {
        ObservingView(publisher: asPublisher(viewModel.output)) { output in
            VStack {
                Text(output.name)
                Text(output.priceCategory)
                // etc

lammertw

class RestaurantDetailViewModelImpl(api: Api, restaurantId: Int): RestaurantDetailViewModel {

    private val _restaurant = api.restaurant(restaurantId)
    private val _reservations = api.restaurantReservations(restaurantId)

    private val _output = combine(_restaurant, _reservations) { restaurantResponse, reservationsResponse ->
        // for simplicity we ignore error handling and exclude specific loading state for when the restaurant is loading
        RestaurantDetailViewModel.Output(
            name = (restaurantResponse as? Response.Success)?.data?.name ?: "Loading or error...",
            priceCategory = (restaurantResponse as? Response.Success)?.data?.priceCategory ?: "Loading or error...",

lammertw

interface RestaurantDetailViewModel {
    val output: CFlow<Output>

    data class Output(
        val name: String,
        val priceCategory: String,
        val reservations: Reservations
    ) {
        sealed class Reservations {
            object Loading: Reservations()

lammertw

struct RestaurantDetailView_Previews: PreviewProvider {
    static var previews: some View {
        InnerView(
            output: RestaurantDetailViewModelOutput(
                name: "My restaurant",
                priceCategory: "Expensive",
                reservations: RestaurantDetailViewModelOutput.ReservationsLoading()
            )
        )
    }

lammertw

struct RestaurantDetailView: View {

    let viewModel: RestaurantDetailViewModel

    var body: some View {
        ObservingView(publisher: asPublisher(viewModel.output), content: InnerView.init)
    }
}

private struct InnerView: View {

lammertw

import Combine
import SwiftUI

import shared

class ObservableRestaurantDetailViewModel: ObservableObject {
    @Published var viewModelOutput: RestaurantDetailViewModelOutput?

    init(viewModel: RestaurantDetailViewModel) {
        asPublisher(viewModel.output)