SwiftUI View - viewDidLoad()?

Question

Trying to load an image after the view loads, the model object driving the view (see MovieDetail below) has a urlString. Because a SwiftUI View element has no life cycle methods (and there's not a view controller driving things) what is the best way to handle this?

The main issue I'm having is no matter which way I try to solve the problem (Binding an object or using a State variable), my View doesn't have the urlString until after it loads...

// movie object struct Movie: Decodable, Identifiable {      let id: String     let title: String     let year: String     let type: String     var posterUrl: String      private enum CodingKeys: String, CodingKey {         case id = "imdbID"         case title = "Title"         case year = "Year"         case type = "Type"         case posterUrl = "Poster"     } } 

// root content list view that navigates to the detail view struct ContentView : View {      var movies: [Movie]      var body: some View {         NavigationView {             List(movies) { movie in                 NavigationButton(destination: MovieDetail(movie: movie)) {                     MovieRow(movie: movie)                 }             }             .navigationBarTitle(Text("Star Wars Movies"))         }     } } 

// detail view that needs to make the asynchronous call struct MovieDetail : View {      let movie: Movie     @State var imageObject = BoundImageObject()      var body: some View {         HStack(alignment: .top) {             VStack {                 Image(uiImage: imageObject.image)                     .scaledToFit()                  Text(movie.title)                     .font(.subheadline)             }         }     } } 

Thanks in advance.

Answer 1

I hope this is helpful. I found a blogpost that talks about doing stuff onAppear for a navigation view.

Idea would be that you bake your service into a BindableObject and subscribe to those updates in your view.

struct SearchView : View {     @State private var query: String = "Swift"     @EnvironmentObject var repoStore: ReposStore      var body: some View {         NavigationView {             List {                 TextField($query, placeholder: Text("type something..."), onCommit: fetch)                 ForEach(repoStore.repos) { repo in                     RepoRow(repo: repo)                 }             }.navigationBarTitle(Text("Search"))         }.onAppear(perform: fetch)     }      private func fetch() {         repoStore.fetch(matching: query)     } } 

import SwiftUI import Combine  class ReposStore: BindableObject {     var repos: [Repo] = [] {         didSet {             didChange.send(self)         }     }      var didChange = PassthroughSubject<ReposStore, Never>()      let service: GithubService     init(service: GithubService) {         self.service = service     }      func fetch(matching query: String) {         service.search(matching: query) { [weak self] result in             DispatchQueue.main.async {                 switch result {                 case .success(let repos): self?.repos = repos                 case .failure: self?.repos = []                 }             }         }     } } 

Credit to: Majid Jabrayilov