Decoding dynamic JSON structure in swift 4

Question

I have the following issue that I\'m not sure how to handle.

My JSON response can look like this:

{ 
  \"data\": {
      \"id\": 7,
      \"         


        

Answer 1

If data can be a single object or an array write a custom initializer which decodes first an array, if a type mismatch error occurs decode a single object. data is declared as an array anyway.

As token appears only in a single object the property is declared as optional.

struct ApiData: Decodable {
    let data : [DataObject]
    let error : String?

    private enum CodingKeys : String, CodingKey { case data, error }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        do {
            data = try container.decode([DataObject].self, forKey: .data)
        } catch DecodingError.typeMismatch {
            data = [try container.decode(DataObject.self, forKey: .data)]
        }
        error = try container.decodeIfPresent(String.self, forKey: .error)
    }
}


struct DataObject: Decodable {
    let userId : Int
    let token : String?

    private enum CodingKeys: String, CodingKey { case userId = "id", token }
}

Edit: Your code to receive the data can be improved. You should add a better error handling to return also all possible errors:

func makeDataTaskWith(with urlRequest: URLRequest, completion: @escaping(ApiData?, Error?) -> Void) {
    let config = URLSessionConfiguration.default
    let session = URLSession(configuration: config)

    session.dataTask(with: urlRequest) {
        (data, response, error) in
        if let error = error { completion(nil, error); return }

        if let responseCode = response as? HTTPURLResponse {
            print("Response has status code: \(responseCode.statusCode)")
        }

        do {
            let retreived = try NetworkManager.shared.decoder.decode(ApiData.self, from: data!)
            completion(retreived, nil)
        } catch {
            print("Decoder error: ", error)
            completion(nil, error)
        }
        }.resume()
}