使用 Codable 解码 JSON，然后填充我的 SwiftUI

Question

I am new to Swift and SwiftUI. I am currently teaching myself how to code (loving it!) through hackingwithswift.com I am currently on Day 60 and I am stuck and not sure what to do from here.

The challenge is to decode some information using Codable and populate SwiftUI.

I created a struct to match the JSON, but when I go to run the app, I keep getting my error "Fetch Failed: Unknown Error" and therefore my UI won't update.

Would someone glance at my code and provide any pointers on where I am going wrong and possibly why? Thank you so much for any suggestions and help, it is much appreciated! Code is posted below.

Cody

import SwiftUI

struct Response: Codable {
    var results: [User]
}

struct User: Codable, Identifiable {
    let id: String
    let isActive: Bool
    let name: String
    let age: Int
    let company: String
    let email: String
    let address: String
    let about: String
    let registered: String
    let tags: [String]
    
    struct FriendRole: Codable {
        let id: String
        let name: String
    }
    
    let friend: [FriendRole]
    
}

struct ContentView: View {
    @State private var results = [User]()
    
    var body: some View {
        List(results, id: \.id) { item in
            VStack(alignment: .leading) {
                Text(item.name)
                    .font(.headline)
                Text(item.address)
            }
        }
    .onAppear(perform: loadData)
    }
    
    func loadData() {
        guard let url = URL(string: "https://www.hackingwithswift.com/samples/friendface.json") else {
            print("Invalid URL")
            return
        }
        
        let request = URLRequest(url: url)
        
        URLSession.shared.dataTask(with: request) { data, response, error in
            if let data = data {
                if let decodedResponse = try? JSONDecoder().decode(Response.self, from: data) {
                    DispatchQueue.main.async {
                        self.results = decodedResponse.results
                    }
                    return
                }
            }
            print("Fetch Failed: \(error?.localizedDescription ?? "Unkown Error").")
        }.resume()
    }
}

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

Answer 1

I'm also new to swiftUI this is how I managed to make it work by using Observable Objects

Here's the structures Since in the json file there is a [ in the very beginning you do not have to create a struct that has a User array you could create a struct and then create a variable of that struct type as an array

here's how I did it

I created separate files for instance for the structures i had a different file for them

here's what I have for my structure file

import Foundation



struct User : Codable, Identifiable {
    let id : String
    let isActive : Bool
    let name : String
    let age : Int
    let company : String
    let email : String
    let address : String
    let about : String
    let registered : String
    let tags = [String]()
    let friends = [Friends]()
}


struct Friends : Codable {
    let id : String
    let name : String
}

I created another file for the observable object class

class JsonChannel : ObservableObject {
    @Published var retVal = [User]()
    func getInfo () {
        guard let url = URL(string: "https://www.hackingwithswift.com/samples/friendface.json") else {return}
        URLSession.shared.dataTask(with: url) { (data, resp, err) in
            if let data = data {
                DispatchQueue.main.async {
                    do {
                        self.retVal = try JSONDecoder().decode([User].self, from: data)
                    }
                    catch {
                        print(error)
                    }
                }
            }
        }.resume()
    }
}

and here's what i have for my contentView file

import SwiftUI

struct ContentView : View {
    @ObservedObject var info = JsonChannel()
    var body: some View {
        VStack {
            Button(action: {
                self.info.getInfo()
            }) {
                Text("click here to get info")
            }
            List {
                ForEach (self.info.retVal) { item in
                    VStack {
                        Text("\(item.name)")
                        Text("\(item.address)")
                    }
                    
                }
            }
        }
    }
}

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