Swift Result Type

struct ContentView: View {
    @State private var output = ""
    
    var body: some View {
        Text(output)
            .task {
                await fetchReadings()
            }
    }
    
    func fetchReadings() async {
        let fetchTask = Task { () -> String in
            let url = URL(string: "https://hws.dev/readings.json")!
            let (data, _) = try await URLSession.shared.data(from: url)
            let readings = try JSONDecoder().decode([Double].self, from: data)
            return "Found \(readings.count) readings"
        }
        let result = await fetchTask.result
        switch result {
        case .success(let str):
            output = str
        case .failure(let error):
            output = "Error: \(error.localizedDescription)"
        }
    }
}

enum NetworkError: Error {
    case badURL, requestFailed, unknown
}

struct ContentView: View {
    
    var body: some View {
        Text("Hello, World!")
            .onAppear {
                self.fetchData(from: "https://www.apple.com") { result in
                    switch result {
                    case .success(let str):
                        print(str)
                    case .failure(let error):
                        switch error {
                        case .badURL:
                            print("Bad URL")
                        case .requestFailed:
                            print("Netwrok problems")
                        case .unknown:
                            print("Unknown error ")
                        }
                    }
                }
            }
    }
    
    func fetchData(from urlString: String, completion: @escaping (Result<String, NetworkError>) -> Void) {
        guard let url = URL(string: urlString) else {
            completion(.failure(.badURL))
            return
        }
        
        URLSession.shared.dataTask(with: url) { data, response, error in
            DispatchQueue.main.async {
                if let data = data {
                    let stringData = String(decoding: data, as: UTF8.self)
                    completion(.success(stringData))
                } else if error != nil {
                    completion(.failure(.requestFailed))
                } else {
                    completion(.failure(.unknown))
                }
            }
        }.resume()
    }
}