How to make an additional API call once inside a detail view? - swift

Question

I'm fetching books from an endpoint as such:
class APIManager: ObservableObject {
#Published var books = [Book]()
func fetchBooks() {
if let url = URL(string: urlEndpoint) {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, response, error) in
if error == nil {
if let safeData = data {
do {
let response = try JSONDecoder().decode([Book].self, from: safeData)
DispatchQueue.main.async {
self.books = response
}
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}
My BookView looks like this:
struct BookView: View {
#ObservedObject var apiManager = APIManager()
var body: some View {
NavigationView {
List {
ForEach(apiManager.books) { book in
NavigationLink(
destination: BookDetailView(id: book.id, chapter: book.chapters),
label: {
HStack {
Text(book.name)
Spacer()
Text(book.testament)
}
})
}.navigationBarTitle("Book Title Here")
}.onAppear {
self.apiManager.fetchBooks()
}
}
}
}
When navigating to BookDetailView - I need to make another API call to fetch additional details about the book (such as chapters), given the book id that is passed here:
...
destination: BookDetailView(id: book.id, chapter: book.chapters)
...
Do I simply repeat the process and make another function in my APIManager class and add another #Published var chapters = [Chapter]()
And inside BookDetailView go
// Loop through each chapter here
// I want to display chapter details in this view
Text("You are viewing book id \(id). Chapter: \(chapter)").onAppear {
self.apiManager.fetchChapterDetails()
}
Doing so returns UIScrollView does not support multiple observers implementing
Whats the procedure here?

Answer 1

I would suggest making a separate ViewModel for the Detail Page. In that ViewModel you can pass in the id of the Book and make a separate API function. Also think about extracting the API Calls into a Service class, which being called from the ViewModel.
The Detail View and ViewModel could look like that...
class BookDetailViewModel: ObservableObject {
let bookId: Int
init(withBookId bookId: Int) {
self.bookId = bookId
}
func fetchBookInfos() {
// ...
}
}
struct BookDetailView: View {
#ObservedObject var viewModel: BookDetailViewModel
var body: some View {
NavigationView {
List {
Text("Book id \(viewModel.bookId)")
}.onAppear {
self.viewModel.fetchBookInfos()
}
}
}
}
When creating the Detail View, pass in the ViewModel.