Writing data to a file with path using NSKeyedArchiver archivedData throws Unrecognized Selector for Swift 4.2 - swift

Question

I am attempting to use the NSKeyedArchiver to write a Codable to disk.
All the questions I could find on the subject using deprecated methods. I can't find any SO questions or tutorials using the Swift 4 syntax.
I am getting the error
-[_SwiftValue encodeWithCoder:]: unrecognized selector sent to instance
Which I am guessing is the try writeData.write(to: fullPath) line in my UsersSession class.
What is the proper way to write data to a file in Swift 4.2?
struct UserObject {
var name : String?
}
extension UserObject : Codable {
enum CodingKeys : String, CodingKey {
case name
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
name = try container.decode(String.self, forKey: .name)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(name, forKey: .name)
}
}
UserSession.swift
class UserSession {
static let shared = UserSession()
let fileName = "userdata.dat"
var user : UserObject?
lazy var fullPath : URL = {
return getDocumentsDirectory().appendingPathComponent(fileName)
}()
private init(){
print("FullPath: \(fullPath)")
user = UserObject()
load()
}
func save(){
guard let u = user else { print("invalid user data to save"); return}
do {
let writeData = try NSKeyedArchiver.archivedData(withRootObject: u, requiringSecureCoding: false)
try writeData.write(to: fullPath)
} catch {
print("Couldn't write user data file")
}
}
func load() {
guard let data = try? Data(contentsOf: fullPath, options: []) else {
print("No data found at location")
save()
return
}
guard let loadedUser = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? UserObject else {
print("Couldn't read user data file.");
return
}
user = loadedUser
}
func getDocumentsDirectory() -> URL {
return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
}
}

Answer 1

Since you are using Codable, you should first encode to Data and then archivedData. Here is the code:
func save(){
guard let u = user else { print("invalid user data to save"); return}
do {
// Encode to Data
let jsonData = try JSONEncoder().encode(u)
let writeData = try NSKeyedArchiver.archivedData(withRootObject: jsonData, requiringSecureCoding: false)
try writeData.write(to: fullPath)
} catch {
print("Couldn't write user data file")
}
}
func load() {
guard let data = try? Data(contentsOf: fullPath, options: []) else {
print("No data found at location")
save()
return
}
guard let loadedUserData = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? Data else {
print("Couldn't read user data file.");
return
}
// Decode Data
user = try? JSONDecoder().decode(UserObject.self, from: loadedUserData)
}