Refresh a SwiftUI View on Back Navigation - swiftui

Question

I have a MainView and DetailView. The MainView displays a list of items. From MainView you can go to DetailView using the push navigation. The DetailView allows to add the item. After adding the new item, I am trying to go back to the MainView and refresh the MainView. It goes back but it never displays the new item unless I restart the app.
I added onAppear on the MainView and I can see it is getting fired. But it still does not update the view.
Here is some code in the MainView:
var body: some View {
List {
ForEach(movieListVM.movies, id: \.id) { movie in
NavigationLink(
destination: AddUpdateMovieScreen(movieId: movie.id),
label: {
MovieCell(movie: movie)
})
}.onDelete(perform: deleteMovie)
}
.listStyle(PlainListStyle())
.navigationTitle("Movies")
.navigationBarItems(trailing: Button("Add Movie") {
isPresented = true
})
.sheet(isPresented: $isPresented, onDismiss: {
movieListVM.populateMovies()
}, content: {
AddUpdateMovieScreen()
})
.onAppear(perform: {
movieListVM.populateMovies()
})
.embedInNavigationView()
Here is the code in the ViewModel:
class MovieListViewModel: ObservableObject {
#Published var movies = [MovieViewModel]()
#Published var updated: Bool = false
func deleteMovie(movie: MovieViewModel) {
let movie = CoreDataManager.shared.getMovieById(id: movie.id)
if let movie = movie {
CoreDataManager.shared.deleteMovie(movie)
}
}
func populateMovies() {
let movies = CoreDataManager.shared.getAllMovies()
for movie in movies {
print(movie.title) // THIS PRINTS THE UPDATE OBJECTS
}
DispatchQueue.main.async {
self.movies = movies.map(MovieViewModel.init) // THIS POPULATES THE movies correctly.
}
}
}
Any ideas why the MainView is not updating, even though I am firing the populateMovies function of the MovieListViewModel.
import SwiftUI
import CoreData
struct AddUpdateMovieScreen: View {
#StateObject private var addMovieVM = AddUpdateMovieViewModel()
#Environment(\.presentationMode) var presentationMode
#State private var movieVS = MovieViewState()
var movieId: NSManagedObjectID?
private func saveOrUpdate() {
do {
if movieId != nil {
// UPDATE IS THE ISSUE I AM TRYING TO RESOLVE
try addMovieVM.update(movieVS)
} else {
addMovieVM.save(movieVS)
}
} catch {
print(error)
}
}
var body: some View {
Form {
TextField("Enter name", text: $movieVS.title)
TextField("Enter director", text: $movieVS.director)
HStack {
Text("Rating")
Spacer()
RatingView(rating: $movieVS.rating)
}
DatePicker("Release Date", selection: $movieVS.releaseDate)
HStack {
Spacer()
Button("Save") {
saveOrUpdate()
presentationMode.wrappedValue.dismiss()
}
Spacer()
}
}
.onAppear(perform: {
// if the movieId is not nil then fetch the movie information
if let movieId = movieId {
// fetch the movie
do {
let movieVM = try addMovieVM.getMovieById(movieId: movieId)
movieVS = MovieViewState.fromMovieViewModel(vm: movieVM)
} catch {
print(error)
}
}
})
.navigationTitle("Add Movie")
.embedInNavigationView()
}
}
struct AddMovieScreen_Previews: PreviewProvider {
static var previews: some View {
AddUpdateMovieScreen()
}
}

Answer 1

Since you don't show your code for "AddUpdateMovieScreen", here are my guesses:
if you are passing "movieListVM" to "AddUpdateMovieScreen" as ObservableObject, then use this:
.sheet(isPresented: $isPresented) {
AddUpdateMovieScreen(movieListVM: movieListVM)
}
and:
struct AddUpdateMovieScreen: View {
#ObservedObject var movieListVM: MovieListViewModel
...
if you are passing "movieListVM" to "AddUpdateMovieScreen" as EnvironmentObject, then use this:
.sheet(isPresented: $isPresented) {
AddUpdateMovieScreen().environment(movieListVM)
}
and:
struct AddUpdateMovieScreen: View {
#EnvironmentObject var movieListVM: MovieListViewModel
...
There is no need for "movieListVM.populateMovies()" in the sheet onDismiss.