Coding

gistfile1.txt

//
//  main.swift
//  TestRecursiveNSArchive
//
//  Created by Helge Hess on 09.12.17.
//  Copyright © 2017 ZeeZide GmbH. All rights reserved.
//

import Foundation

class Customer : NSObject, NSCoding {
  let name: String
  var card: CreditCard?
  init(name: String) {
    self.name = name
  }
  deinit { print("\(name) is being deinitialized") }
  
  public func encode(with aCoder: NSCoder) {
    aCoder.encode(name, forKey: "name")
    aCoder.encode(card, forKey: "card")
  }
  
  required public init?(coder aDecoder: NSCoder) {
    guard let name = aDecoder.decodeObject(forKey: "name") as? String
      else { return nil }
    
    self.name = name
    card = aDecoder.decodeObject(forKey: "card") as? CreditCard
  }
  
  override var description: String {
    return "<Author: name=\(name) card=\(card as Optional)>"
  }
}

class CreditCard : NSObject, NSCoding {
  // replace UInt64 w/ Int64 since there is no matching coder func
  let number: Int64
  unowned let customer: Customer
  init(number: Int64, customer: Customer) {
    self.number   = number
    self.customer = customer
  }
  deinit { print("Card #\(number) is being deinitialized") }
  
  public func encode(with aCoder: NSCoder) {
    aCoder.encode(number,   forKey: "number")
    aCoder.encode(customer, forKey: "customer")
  }
  
  required public init?(coder aDecoder: NSCoder) {
    guard let customer = aDecoder.decodeObject(forKey: "customer") as? Customer
      else { return nil }
    self.number   = aDecoder.decodeInt64(forKey: "number")
    self.customer = customer
  }

  override var description: String {
    return "<CC: number=\(number)>"
  }
}

let john = Customer(name: "John Appleseed")
john.card = CreditCard(number: 1234_5678_9012_3456, customer: john)
print("john: \(john)")

let data = NSKeyedArchiver.archivedData(withRootObject: john)
let newJohn = NSKeyedUnarchiver.unarchiveObject(with: data)!
print("newJohn: \(newJohn)")

Gives:

john: <Author: name=John Appleseed card=Optional(<CC: number=1234567890123456>)>
newJohn: <Author: name=John Appleseed card=Optional(<CC: number=1234567890123456>)>

BTW: there is also a bug in NSCoder or NSUnarchiver. It sends replacementObjectForCoder: w/o checking whether the instance has it or not (only reason I inherit from NSObject above). That should either be part of NSCoding then, or be optional.