SOLVED: How to decode JSON response with different type

@akrambazina

Aug '21

Hello HWS Forum

I am using an API with have different JSON response type. for example of success, the response is :

{
    "status": "success",
    "result": {
        "useruuid": "ab872795-ee32-11eb",
        "usertoken": "DbXapngqtEynm6EKja3"
    }
}

in case of error, the response is like :

{
    "status": "error",
    "result": "token mismatch"
}

the task code handling the request have a ResponseType. the code is:

class func taskForPOSTRequest<ResponseType: Decodable>(url: URL, responseType: ResponseType.Type, body: String, completion: @escaping (ResponseType?, Error?) -> Void) {
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.httpBody = body.data(using: .utf8)
        //request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            guard let data = data else {
                DispatchQueue.main.async {
                    completion(nil, error)
                }
                return
            }
            let decoder = JSONDecoder()
            do {
                let responseObject = try decoder.decode(ResponseType.self, from: data)
                DispatchQueue.main.async {
                    completion(responseObject, nil)
                }
            } catch {
                DispatchQueue.main.async {
                    completion(nil, error)
                }
            }
        }
        task.resume()
    }

How can I handle both response cases of the result node.

Thanks

@roosterboy HWS+

Aug '21

Here's one way you can do it:

struct User: Decodable {
    let userUUID: UUID
    let userToken: String

    enum CodingKeys: String, CodingKey {
        case userUUID = "useruuid"
        case userToken = "usertoken"
    }
}

enum ResponseType: Decodable {
    case user(User)
    case error(String)

    enum CodingKeys: String, CodingKey {
        case status
        case result
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let status = try container.decode(String.self, forKey: .status)

        switch status {
        case "success":
            let user = try container.decode(User.self, forKey: .result)
            self = .user(user)
        case "error":
            let errorString = try container.decode(String.self, forKey: .result)
            self = .error(errorString)
        default:
            fatalError("We got a weird case")
        }
    }
}

You would then switch over the value of the ResponseType parameter to the completion handler:

switch response {
case .user(let user):
    //you've got a User object here
case .error(let error):
    //you've got an error string here
}

@akrambazina

Aug '21

brilliant answer.

thank you so much. it work like a charm.

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