Decoding this simple JSON struct is not working - swift

Question

I have a simple model which I defined to decode a struct.
But it is failing at decoding.
Can any one tell me what i am doing wrong?
struct Model: Codable {
let firstName: String
let lastName: String
let age: Int
enum Codingkeys: String, CodingKey {
case firstName = "first_name"
case lastName = "last_name"
case age
}
}
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let session = URLSession.shared
let url = URL(string: "https://learnappmaking.com/ex/users.json")!
let task = session.dataTask(with: url) { (data, response, error) in
let decoder = JSONDecoder()
let d = try! decoder.decode([Model].self, from: data!) //fails here
print(d)
}
task.resume()
}
}
I double checked to see if the json was correct, but it still fails to decode.
Error shown
Thread 5: Fatal error: 'try!' expression unexpectedly raised an error:
Swift.DecodingError.keyNotFound(CodingKeys(stringValue: "firstName",
intValue: nil), Swift.DecodingError.Context(codingPath:
[_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No
value associated with key CodingKeys(stringValue: \"firstName\",
intValue: nil) (\"firstName\").", underlyingError: nil))
It keeps searching for firstName but i specifically have a enum to check for first_name.
This is the JSON Payload
[
{
"first_name": "Ford",
"last_name": "Prefect",
"age": 5000
},
{
"first_name": "Zaphod",
"last_name": "Beeblebrox",
"age": 999
},
{
"first_name": "Arthur",
"last_name": "Dent",
"age": 42
},
{
"first_name": "Trillian",
"last_name": "Astra",
"age": 1234
}
]
I know I can add decoder.keyDecodingStrategy = .convertFromSnakeCase but I want to know why the existing code is not working?

Answer 1

The code is correct, but apparently there is some problem with your model (although convertFromSnakeCase does work)
I retyped the struct and the error went away. Please copy and paste this
struct Model : Decodable {
let firstName : String
let lastName : String
let age : Int
private enum CodingKeys : String, CodingKey { case firstName = "first_name", lastName = "last_name", age }
}

Answer 2

Some of the values are optional, to be safe make all let as optional, It will work for sure.
struct Model: Codable {
let firstName: String?
let lastName: String?
let age: Int?
enum Codingkeys: String, CodingKey {
case firstName = "first_name"
case lastName = "last_name"
case age
}
}