Swift - JSON decoding - json

Question

I have a JSON response from an api call. The problem is I get different JSON responses depending on whether the user has entered the correct credentials or not. My question is how do I read and decode these responses to a useable struct and what is the best way to go about decoding these different responses. one thing I noticed is both response have a common "isSuccess" that may be useful. I have little to no experience with swift or reading JSON so this is all a learning experience for me.
This is the response for successful login
{"result":{"login":{"isAuthorized":true,"isEmpty":false,"userName":{"isEmpty":false,"name":{"firstName":"Jason","lastName":"Test","displayName":"Test, Jason","isEmpty":false,"fullName":"Jason Test"},"canDelete":false,"id":5793,"canModify":false},"username":"test#testable.com"},"parameters":{"isEmpty":false,"keep_logged_in_indicator":false,"username":"test#testable.com"}},"isAuthorized":true,"version":{"major":"2021","minor":"004","fix":"04","display":"2021.004.04","isEmpty":false},"isSystemDown":false,"timestamp":"2021-07-28T02:47:33Z","isSuccess":true}
This is the response for failure
{"isAuthorized":true,"version":{"major":"2021","minor":"004","fix":"04","display":"2021.004.04","isEmpty":false},"isSystemDown":false,"errors":[{"password":"Unable to login as 'test#testable.com'"}],"timestamp":"2021-07-28T02:47:05Z","isSuccess":false}
This is the code I have written for my api calls
func request<T: Decodable>(endPoint: EndPoint, method: Method, parameters: [String: Any]? = nil, completion: #escaping(Result<T, Error>) -> Void) {
// Creates a urlRequest
guard let request = createRequest(endPoint: endPoint, method: method, parameters: parameters) else {
completion(.failure(AppError.invalidUrl))
return
}
let session = URLSession.shared
session.dataTask(with: request) { data, response, error in
var results: Result<Data, Error>?
guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
completion(.failure(AppError.badStatusCode))
return
}
if let response = response {
// Gets the JSESSIONID
let cookieName = "JSESSIONID"
if let cookie = HTTPCookieStorage.shared.cookies?.first(where: { $0.name == cookieName }) {
debugPrint("\(cookieName): \(cookie.value)")
}
print(response)
}
if let data = data {
results = .success(data)
// Converts data to readable String
let responseString = String(data: data, encoding: .utf8) ?? "unable to convert to readable String"
print("Server Response: \(responseString.description)")
} else if let error = error {
results = .failure(error)
print("Server Error: \(error.localizedDescription)")
}
DispatchQueue.main.async {
self.handleResponse(result: results, completion: completion)
}
}.resume()
}
private func handleResponse<T: Decodable>(result: Result<Data, Error>?, completion: (Result<T, Error>) -> Void) {
guard let result = result else {
completion(.failure(AppError.unknownError))
return
}
switch result {
case .success(let data):
do {
let json = try JSONSerialization.jsonObject(with: data, options: [])
print("Server JsonObject response: \(json)")
} catch {
completion(.failure(AppError.errorDecoding))
}
let decoder = JSONDecoder()
// Decodes that json data
do {
} catch {
}
case .failure(let error):
completion(.failure(error))
}
}
Im mostly interesting in being able to display the json error that occurs when credentials are incorrect. The deadline for my project Is slowing approaching and any help or suggestions would be much appreciated.

Answer 1

You can use Swift's Result type to differentiate a successful result from a failed result.
The Result type is not decodable by default so you will need to write a custom decoder like this:
struct Response: Decodable {
let result: Swift.Result<Result, Errors>
enum CodingKeys: String, CodingKey {
case isSuccess
case errors
case result
}
struct Result: Codable {
let login: Login
struct Login: Codable {
let isAuthorized: Bool
}
}
struct Errors: Error {
let contents: [[String: String]]
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
if try container.decode(Bool.self, forKey: .isSuccess) {
result = .success(try container.decode(Result.self, forKey: .result))
} else {
result = .failure(
Errors(contents: try container.decode([[String: String]].self, forKey: .errors))
)
}
}
}