Unable to get the data from a nested json swift - swift

Question

I'm learning swift.
I have a json from server.
[
{
"dId": 1,
"vendor": {
"vendorId": 1,
"name": "Gems",
"about": "Get Good quality stones",
"address": "JacksonVille Road",
"latitude": 12.232323,
"longitude": 77.230802,
},
"name": "Gems Delight",
}
]
I'm unable to parse this json and get the data from lat and lon and name from vendor.
My url method and my for loop how can I exactly get the latitude and longitude from the loop and put them on the map ?
My View did load method
override func viewDidLoad() {
super.viewDidLoad()
guard let gitUrl = URL(string: "localhost:8080/deals") else { return }
URLSession.shared.dataTask(with: gitUrl) { (data, response
, error) in
guard let data = data else { return }
do {
let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers)
var lat:Double
var lon:Double
var nam = ""
for items in json as! [AnyObject]{
// let te = type(of: items)
// print(te)
let new = items["vendor"]
for (it,key) in new as! [String:Any]{
// print(it,key)
// print(it["longitude"])
if it == "longitude"{
print(it,key)
lon = key as! Double
}
if it == "latitude"{
print(it,key)
lat = key as! Double
}
if it == "name"{
nam = key as! String
}
if (nam.isEmpty == false){
print("falsdalsdasldasd")
self.locationManager.delegate = self
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()
let camera = GMSCameraPosition.camera(withLatitude:lat, longitude:lon, zoom: 4.0)
let subView = GMSMapView.map(withFrame: self.view.bounds,camera:camera)
let marker = GMSMarker()
marker.position = CLLocationCoordinate2D(latitude:lat, longitude:lon)
marker.title = nam
// marker.snippet = "Australia"
marker.map = subView
self.mapView.addSubview(subView)
}
// print(it["longitude"])
}
// let te = type(of: items)
// for it in new as![AnyObject]{
//// print(it"])
// print(it)
//
// }
// print(items["vendor"].["latitude"])
// print(items.vendor)
// print(items[""])
// let nam = items["name"];
// let desc = items["description"];
// self.locationNames.append(nam as! String)
// self.locationDescription.append(desc as! String)
//
}
// self.colecVw.delegate = self
// self.colecVw.dataSource = self
// self.colecVw.reloadData()
// }
} catch let err {
print("Err", err)
}
}.resume()
print("coming here")
// Create a GMSCameraPosition that tells the map to display the
// coordinate -33.86,151.20 at zoom level 6.
// let mapView = GMSMapView(frame: CGRect(x: 0, y: 64, width: self.currentDeviceSize.width, height: self.bottomBgView.frame.minY - 64))
// view = mapView
//
// // Creates a marker in the center of the map.
// let marker = GMSMarker()
// marker.position = CLLocationCoordinate2D(latitude: -33.86, longitude: 151.20)
// marker.title = "Sydney"
// marker.snippet = "Australia"
// marker.map = mapView
}
Please help me as I'm learning to code my code might not be correct can please dont mind and load the data of lat and long onto the map. Should I construct an object and put them there ?
Variable 'lon' used before being initialized
Variable 'lat' used before being initialized
This is the error I get from the code.

Answer 1

The errors occur because lat and lon must have a value in the line
let camera = GMSCameraPosition.camera(withLatitude:lat, longitude:lon, zoom: 4.0)
which is not guaranteed if the key comparisons fail.
The condition is fulfilled if you write
var lat = 0.0 // The type Double is inferred
var lon = 0.0
But rather than enumerating the dictionary get the values for the keys directly and safely with optional binding
do {
// no mutableContainers !!
let json = try JSONSerialization.jsonObject(with: data) as! [[String:Any]]
for item in json {
if let vendor = item["vendor"] as? [String:Any],
let lat = vendor["latitude"] as? Double,
let lon = vendor["longitude"] as? Double,
let name = item["name"] as? String, !name.isEmpty {
print("falsdalsdasldasd")
// self.locationManager.delegate = self
// self.locationManager.requestWhenInUseAuthorization()
// self.locationManager.startUpdatingLocation()
let camera = GMSCameraPosition.camera(withLatitude:lat, longitude:lon, zoom: 4.0)
let subView = GMSMapView.map(withFrame: self.view.bounds,camera:camera)
let marker = GMSMarker()
marker.position = CLLocationCoordinate2D(latitude:lat, longitude:lon)
marker.title = name
marker.map = subView
self.mapView.addSubview(subView)
}
}
} catch {
print("Err", error)
}
And it's nonsensical to call the LocationManager methods in each iteration. Call them once at the beginning of viewDidLoad
override func viewDidLoad() {
super.viewDidLoad()
self.locationManager.delegate = self
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()
...

Answer 2

You can try
struct Root: Codable {
let dID: Int
let vendor: Vendor
let name: String
enum CodingKeys: String, CodingKey {
case dID = "dId"
case vendor, name
}
}
struct Vendor: Codable {
let vendorID: Int
let name, about, address: String
let latitude, longitude: Double
enum CodingKeys: String, CodingKey {
case vendorID = "vendorId"
case name, about, address, latitude, longitude
}
}
--
let arr = try? JSONDecoder().decode([Root].self, from:data)
print(arr?.forEach {$0.vendor.latitude })

Answer 3

See this one
let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers)
Pass json to
if let data = json as? NSArray {
for data in data {
if let data = data as? [String: AnyObject] {
let dataID = data["dId"] as? Int
if let data = data[“vendor”] as? [String: AnyObject] {
let vendorID = data["vendorId"] as? Int
}
}
}
}