Hi all, I've been working through the 100 Days of SwiftUI course and am trying to stretch my API legs as an extension of the Friendface project (Day 54).

I'm struggling when decoding a dictionary, rather than an array as we have in the Friendface project. The URL at the link (https://jsonplaceholder.typicode.com/todos/1) only has four items: { "userId": 1, "id": 1, "title": "delectus aut autem", "completed": false }

The code doesn't generate any errors, but when I hit run I see the "Download failed" error printed. I suspect this is because I'm attempting to decode a [User].self array rather than a User.self dictionary, but making that update (and a similar update to the @State var) sets off a series of errors.

Any help appreciated, I've spent enough time on this to feel pretty dumb right now.

import SwiftUI

struct User: Identifiable, Codable {
    let id: Int
    let title: String
}

struct ContentView: View {
    @State private var users = [User]()

    var body: some View {
        NavigationView {
            List(users) { user in
                NavigationLink {
                    Text(user.title)
                } label: {
                    Text(user.title)
                }
            }
            .navigationTitle("Friendface")
            .task {
                await fetchUsers()
            }
        }
    }

    func fetchUsers() async {
        // Don't re-fetch data if we already have it
        guard users.isEmpty else { return }

        do {
            let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")!
            let (data, _) = try await URLSession.shared.data(from: url)

            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = .iso8601
            users = try decoder.decode([User].self, from: data)
        } catch {
            print("Download failed")
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

The code doesn't generate any errors, but when I hit run I see the "Download failed" error printed. I suspect this is because I'm attempting to decode a [User].self array rather than a User.self dictionary, but making that update (and a similar update to the @State var) sets off a series of errors.

That is exactly the problem. What errors are you seeing pop up as a result?

This works just fine:

import SwiftUI

struct User: Identifiable, Codable {
    let id: Int
    let title: String
}

struct DecodedUserView: View {
    @State private var user = User(id: 0, title: "")

    var body: some View {
        NavigationView {
            NavigationLink {
                Text(user.title)
            } label: {
                Text(user.title)
            }
            .navigationTitle("Friendface")
            .task {
                await fetchUsers()
            }
        }
    }

    func fetchUsers() async {
        do {
            let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")!
            let (data, _) = try await URLSession.shared.data(from: url)

            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = .iso8601
            user = try decoder.decode(User.self, from: data)
        } catch {
            //give us some real error information
            print(error)
        }
    }
}

struct DecodedUserView_Previews: PreviewProvider {
    static var previews: some View {
        DecodedUserView()
    }
}

Brilliant, thanks! Thanks for the quick code rehab.

The errors I was seeing on my code before when attempting my dictionary conversion... On the List code: "Initializer 'init(:rowContent:)' requires that 'User' conform to 'RandomAccessCollection'" On the Guard code: "Cannot convert value of type 'Binding<Subject>' to expected condition type 'Bool'" "Referencing subscript 'subscript(dynamicMember:)' requires wrapper 'Binding<User>'" "Value of type 'User' has no dynamic member 'isEmpty' using key path from root type 'User'"

I suspect for the List error, List is incompatible with a dictionary as it's meant to serve up an array of data? Guard might be a similar story - it's meant to check if there's an empty array of data - but this is a dictionary which must not have the same "isEmpty" checker?

Last question for you - is it required to set initial values for the 'user' var, as you did in your @State above? It looked like for the Friendface project, Paul set his initial array as empty. When I try pulling those initial conditions out of my @State private var user (so, user = User()), Xcode complains it needs a value - fair. Then when I try "user: User" instead, the errors show up in the Previews section ("'ContentView' initializer is inaccessible due to 'private' protection level", "Missing argument for parameter 'user' in call").