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When I do an API call and get data back it cannot be decoded into my struct properly.

The error I get is:

failed to convert valueNotFound(Swift.Int, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "data", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "newDeathsByDeathDate", intValue: nil)], debugDescription: "Expected Int value but found null instead.", underlyingError: nil))

My Code is:

override func viewDidLoad() {
        super.viewDidLoad()
        let url = """
https://api.coronavirus.data.gov.uk/v1/data?filters=areaType=nation;areaName=england&structure=%7b%22date%22:%22date%22,%22areaName%22:%22areaName%22,%22areaCode%22:%22areaCode%22,%22newCasesByPublishDate%22:%22newCasesByPublishDate%22,%22cumCasesByPublishDate%22:%22cumCasesByPublishDate%22,%22newDeathsByDeathDate%22:%22newDeathsByDeathDate%22,%22cumDeathsByDeathDate%22:%22cumDeathsByDeathDate%22%7d
        print(url)
        print(NSURL(string: url))
        getData(from: url)
        // Do any additional setup after loading the view.
    private func getData(from url: String) {
        guard let theURL = URL(string: url) else { print ("oops"); return }
        let getfromurl = URLSession.shared.dataTask(with: theURL, completionHandler: {data, response, error in
            guard let data = data, error == nil else{
                print("Something Went Wrong")
                return
            //Have data
            var result: Response?
                result = try JSONDecoder().decode(Response.self, from: data)
            catch{
                print("failed to convert \(error)")
            guard let json = result else {
                return
            print(json.data)
        getfromurl.resume()
My Structs are:
struct Response: Codable {
    let data: [MyData]
struct MyData: Codable{
    let date: String
    let areaName: String
    let areaCode: String
    let newCasesByPublishDate: Int
    let cumCasesByPublishDate: Int
    let newDeathsByDeathDate: Int
    let cumDeathsByDeathDate: Int
                clearly in your struct newDeathsByDeathDate is an Int not Int? so while decoding the json it expected the Int value for key newDeathsByDeathDate but it found nil and because your declaration said it needs to have an Int value it failed. I am not sure how much of the response matches your struct, are u entirely sure all keys in json appropriately  matches keys in struct? Is this the actual hierarchy ? and are u sure it needs to return Int and not Int? or String or double or anything else? if you need custom mapping you might need to override init(from decoder:
– Sandeep Bhandari
                Feb 3, 2021 at 9:27
Please look closely at the JSON, the values for keys newDeathsByDeathDate and cumDeathsByDeathDate can be null.
Make the type of the corresponding struct members optional
struct MyData: Codable{
    let date: String
    let areaName: String
    let areaCode: String
    let newCasesByPublishDate: Int
    let cumCasesByPublishDate: Int?
    let newDeathsByDeathDate: Int?
    let cumDeathsByDeathDate: Int?
Alternatively – to keep non-optional values – decode the JSON manually and set the values to 0 if they are null
struct MyData : Decodable {
    let date, areaName, areaCode: String
    let newCasesByPublishDate, cumCasesByPublishDate : Int
    let newDeathsByDeathDate, cumDeathsByDeathDate: Int
    private enum CodingKeys : String, CodingKey { case date, areaName, areaCode, newCasesByPublishDate, cumCasesByPublishDate, newDeathsByDeathDate, cumDeathsByDeathDate }
    init(from decoder : Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        date = try container.decode(String.self, forKey: .date)
        areaName = try container.decode(String.self, forKey: .areaName)
        areaCode = try container.decode(String.self, forKey: .areaCode)
        newCasesByPublishDate = (try? container.decode(Int.self, forKey: .newCasesByPublishDate)) ?? 0
        cumCasesByPublishDate = (try? container.decode(Int.self, forKey: .cumCasesByPublishDate)) ?? 0
        newDeathsByDeathDate = (try? container.decode(Int.self, forKey: .newDeathsByDeathDate)) ?? 0
        cumDeathsByDeathDate = (try? container.decode(Int.self, forKey: .cumDeathsByDeathDate)) ?? 0
And again, don't ignore useful error messages by printing something meaningless
Replace
print("Something Went Wrong")
print("An error occured:", error!)
                Just make everything optional, because it seems like everything might be missing. Or go with a dictionary approach like stackoverflow.com/questions/44603248 (see answer by Vasily)
– Andreas Oetjen
                Feb 3, 2021 at 9:39
        
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