NSKeyedArchiver.archivedData does not work in Swift 3 iOS

Question

When try to encode my custom object in iOS swift get this error from Xcode 8.3

unrecognized selector sent to instance 0x60800166fe80 *** -[NSKeyedArchiver dealloc]: warning: NSKeyedArchiver deallocated without having had -finishEncoding called on it.

And my code like this:

import UIKit import Foundation

class Place: NSObject {

    func setCustomObject(CustomObject obj:Any,Key key:String) {

        let encodedObject : Data = NSKeyedArchiver.archivedData(withRootObject: obj)
        UserDefaults.standard.set(encodedObject, forKey: key)

    }
}

Answer 1

Here's an example how to make an object to conform to NSCoding. Basically you need to provide implementation of two methods - required convenience init?(coder decoder: NSCoder) and encode(with aCoder: NSCoder)

class Book: NSObject, NSCoding {
  var title: String?
  var pageCount: Int?

  // Memberwise initializer
  init(title: String,pageCount: Int) {
   self.title = title
   self.pageCount = pageCount
  }

  // MARK: NSCoding


  // Here you will try to initialize an object from archve using keys you did set in `encode` method.
  required convenience init?(coder decoder: NSCoder) {
    guard let title = decoder.decodeObject(forKey: "title") as? String else { return nil }

    self.init(title: title, pageCount: decoder.decodeInteger(forKey: "pageCount"))
  }

  // Here you need to set properties to specific keys in archive
  func encode(with aCoder: NSCoder) {
    aCoder.encode(self.title, forKey: "title")
    aCoder.encodeCInt(Int32(self.pageCount), forKey: "pageCount")
  }
}

Also I would recommend changing your setCustomObject method to this:

func setCustomObject(obj:NSCoding, key:String) {
  let encodedObject : Data = NSKeyedArchiver.archivedData(withRootObject: obj)
  UserDefaults.standard.set(encodedObject, forKey: key)
}

This way compiler prevent you passing NSKeyedArchiver an object that does not conform to NSCoding protocol.

If you don't want to provide all properties in the init method you can use default values:

init(title : String? = nil, pageCount: Int? = nil){
  self.title = title
  self.pageCount = pageCount
}

Now you can just init your object without any properties. Like that Book()