在 Swift 中获取和解码未知错误

Question

我正在尝试获取数据并将其解码为结构，然后在列表中显示该数据。我使用 quicktype.io 将 JSON 解析为 Swift。这部分好像还行。

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

struct User: Codable {
    let id: String
    let isActive: Bool
    let name: String
    let age: Int
    let company, email, address, about: String
    let registered: Date
    let tags: [String]
    let friends: [Friend]
}

struct Friend: Codable {
    let id, name: String
}

这是代码的其余部分，我在其中尝试解码数据（发生错误的地方）。这里是 link 到 JSON.

struct ContentView: View {
    @State private var users = [User]()
    var body: some View {
            List {
                ForEach(users, id: \.id) { user in
                    Text(user.name)
                }
            }.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) {
                    // we have good data – go back to the main thread
                    DispatchQueue.main.async {
                        // update our UI
                        print(decodedResponse.results)
                        users = decodedResponse.results
                    }

                    // everything is good, so we can exit
                    return
                }
            }
            // if we're still here it means there was a problem
            print("Fetch failed: \(error?.localizedDescription ?? "Unknown error")")
        }.resume()
    }
}

Answer 1

您必须根据类型 [User] 而不是 Response 进行解码。查看响应，您会发现顶级 JSON 是 Array，而不是 Dictionary。此外，更新您的代码以获得有意义的错误消息。使用 do try catch 语法代替 if let try?.

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 {
            do {
                let decoder = JSONDecoder()
                decoder.dateDecodingStrategy = .iso8601
                let users = try decoder.decode([User].self, from: data)
                DispatchQueue.main.async {
                    print(users)
                    self.users = users
                }
            } catch {
                print(error)
            }
        } else {
            // if we're still here it means there was a problem
            print("Fetch failed: \(error?.localizedDescription ?? "Unknown error")")
        }
    }.resume()
}

更新：另外，需要添加dateDecodingStrategy才能使解码正常工作。

在 Swift 中获取和解码未知错误

Fetching and decoding unkwown error in Swift

swift

swiftui

urlsession

jsondecoder