how to parse this complex nested Json - json

Question

The Json is valid but I m getting nil with below code and struct for the returned json.
problem encountered:
at JSonDecoder.decode() : it returned this error msg:
keyNotFound(CodingKeys(stringValue: "items", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "items", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: "items", intValue: nil) ("items").", underlyingError: nil))
How to get these a) image b) location from the Json
Thanks
here the code
func getJsonMapData(){
guard let mapUrl = URL(string: "https://xxxxxx/traffic-images") else { return }
URLSession.shared.dataTask(with: mapUrl) { (data, response, error) in
guard error == nil else { return}
guard let data = data else { return}
//- problem:
do {
let LocationArrDict = try JSONDecoder().decode([String:[Location]].self, from: data)else{
print(LocationArrDict)
} catch {
print(error)
}
}.resume()
}
//------------- return Json String:
{
"items":[
{
"timestamp":"2020-12-05T08:45:43+08:00",
"cameras":[
{
"timestamp":"2020-11-05T08:42:43+08:00",
"image":"https://xxxxxxxxx/traffic-images/2020/12/2ab06cd8-4dcf-434c-b758-804e690e57db.jpg",
"location":{
"latitude":1.29531332,
"longitude":103.871146
},
"camera_id":"1001",
"image_metadata":{
"height":240,
"width":320,
"md5":"c9686a013f3a2ed4af61260811661fc4"
}
},
{
"timestamp":"2020-11-05T08:42:43+08:00",
"image":"https://xxxxxxxxxx/traffic-images/2020/12/9f6d307e-8b05-414d-b27d-bf1414aa2cc7.jpg",
"location":{
"latitude":1.319541067,
"longitude":103.8785627
},
"camera_id":"1002",
"image_metadata":{
"height":240,
"width":320,
"md5":"78060d8fbdd241adf43a2f1ae5d252b1"
}
},
........
{
"timestamp":"2020-12-05T08:42:43+08:00",
"image":"https://xxxxxx/traffic-images/2020/12/98f64fe6-5985-4a8a-852f-0be24b0a6271.jpg",
"location":{
"latitude":1.41270056,
"longitude":103.80642712
},
"camera_id":"9706",
"image_metadata":{
"height":360,
"width":640,
"md5":"f63d54176620fa1d9896fa438b3cc753"
}
}
]
}
],
"api_info":{
"status":"healthy"
}
}
//------------ struct for the return Json result:
// MARK: - Location
struct Location: Codable {
let items: [Item]
let apiInfo: APIInfo
enum CodingKeys: String, CodingKey {
case items
case apiInfo = "api_info"
}
}
// MARK: - APIInfo
struct APIInfo: Codable {
let status: String
}
// MARK: - Item
struct Item: Codable {
let timestamp: Date
let cameras: [Camera]
}
// MARK: - Camera
struct Camera: Codable {
let timestamp: Date
let image: String
let location: LocationClass
let cameraID: String
let imageMetadata: ImageMetadata
enum CodingKeys: String, CodingKey {
case timestamp, image, location
case cameraID = "camera_id"
case imageMetadata = "image_metadata"
}
}
// MARK: - ImageMetadata
struct ImageMetadata: Codable {
let height, width: Int
let md5: String
}
// MARK: - LocationClass
struct LocationClass: Codable {
let latitude, longitude: Double
}
``

Answer 1

Error #1: The type to be decoded is wrong it must be Location.self.
Error #2: To decode the ISO date as Date you have to add the .iso8601 date decoding strategy.
do {
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let locationArrDict = try decoder.decode(Location.self, from: data)
print(locationArrDict)
} catch {
print(error)
}
And you could decode the strings representing an URL directly to URL

Answer 2

You have to create your data models and describe them as the response you expect to receive. I will just give you a brief example based on your json how you would decode it.
First of all in order to decode a JSON using JSONDecoder your models have to conform to Decodable protocol. Then you have to create those models.
struct Item: Decodable {
let timestamp: Date
// let cameras: [...]
}
struct ApiInfo: Decodable {
enum Status: String, Decodable {
case healthy
}
let status: Status
}
struct Response: Decodable {
let items: [Item]
let apiInfo: ApiInfo
}
Then you have to configure your JSONDecoder and decode that JSON. As we can see clearly, your JSON uses snake_case naming convention and that is not the default one for JSONDecoder so you have to set it. Same also applies for the dates - it is used iso8601 standard of representation.
let jsonDecoder = JSONDecoder()
jsonDecoder.dateDecodingStrategy = .iso8601
jsonDecoder.keyDecodingStrategy = .convertFromSnakeCase
Finally, you have you decode it.
do {
let response = try jsonDecoder.decode(Response.self, from: jsonData)
print(response)
} catch {
print(error)
}