What is wrong with the implementation of NSCoding protocol in Swift - objective-c

Question

I thought I'd be cautious and try out Swift on an existing Obj-C project by converting one class. And a small, simple one at that. Oh dear.
Transliterating the original obj-c into Swift should be straightforward and so it seemed. Unfortunately, whilst the encoder to persistent store seems to work, it crashes with an EXC_BREAKPOINT error at the first line of the init coder.
IF (and the caps are intentional) NSCoding/Swift gives the same persistent content as NSCoding/ObjC, then my all obj-c version should be able to read what is encoded by Swift and vice versa. This proves not to be the case - and my perfectly-functioning obj-c version crashes out when it tries to read the persistent store from the Swift version. Surely, if NSCoding is implemented correctly, it ought to generate something in one that is readable in t'other? Otherwise, there ought to be separate NSCodingSwift and NSCodingObjC protocols?
So, to summarise, I can read/write in obj-c. I can't write/obj-c and read/swift and I can write/swift read/obj-c and I can't read/write in swift.
Here are the two versions:
let keyBeaconItemNameKey = "name"
let keyBeaconItemUUIDKey = "uuid"
let keyBeaconItemMajorValueKey = "major"
let keyBeaconItemMinorValueKey = "minor"
import UIKit
import CoreLocation
class SMBeaconItem : NSObject, NSCoding
{
var name : String!
var uuid : NSUUID!
var major : NSNumber!
var minor : NSNumber!
init(newName : String, newUUID : NSUUID, newMajor : NSNumber, newMinor : NSNumber )
{
name = newName
uuid = newUUID
major = newMajor
minor = newMinor
}
init( coder decoder : NSCoder!)
{
name = decoder.decodeObjectForKey(keyBeaconItemNameKey) as String
uuid = decoder.decodeObjectForKey(keyBeaconItemUUIDKey) as NSUUID
major = decoder.decodeObjectForKey(keyBeaconItemMajorValueKey) as NSNumber
minor = decoder.decodeObjectForKey(keyBeaconItemMinorValueKey) as NSNumber
}
func encodeWithCoder( encoder: NSCoder!)
{
encoder.encodeObject(name, forKey:keyBeaconItemNameKey)
encoder.encodeObject(uuid, forKey:keyBeaconItemUUIDKey)
encoder.encodeObject(major, forKey:keyBeaconItemMajorValueKey)
encoder.encodeObject(minor, forKey:keyBeaconItemMinorValueKey)
}
}
And the working original:
#implementation SMBeaconItem
- (instancetype)initWithName:(NSString *)name uuid:(NSUUID *)uuid major:(CLBeaconMajorValue)major minor:(CLBeaconMinorValue)minor
{
self = [super init];
if (!self)
{
return nil;
}
_name = name;
_uuid = uuid;
_majorValue = major;
_minorValue = minor;
return self;
}
#pragma mark - Persistence
- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
self = [super init];
if (!self)
{
return nil;
}
_name = [aDecoder decodeObjectForKey:keyBeaconItemNameKey];
_uuid = [aDecoder decodeObjectForKey:keyBeaconItemUUIDKey];
_majorValue = [[aDecoder decodeObjectForKey:keyBeaconItemMajorValueKey] unsignedIntegerValue];
_minorValue = [[aDecoder decodeObjectForKey:keyBeaconItemMinorValueKey] unsignedIntegerValue];
return self;
}
- (void)encodeWithCoder:(NSCoder *)aCoder
{
[aCoder encodeObject:self.name forKey:keyBeaconItemNameKey];
[aCoder encodeObject:self.uuid forKey:keyBeaconItemUUIDKey];
[aCoder encodeObject:[NSNumber numberWithUnsignedInteger:self.majorValue] forKey:keyBeaconItemMajorValueKey];
[aCoder encodeObject:[NSNumber numberWithUnsignedInteger:self.minorValue] forKey:keyBeaconItemMinorValueKey];
}
#end
Thanks for any help you can give.

Answer 1

The only thing that stands out to me is that you're using String instead of NSString as the name's type. In the betas Apple has been putting out, String (strangely) is not a one-for-one replacement of NSString. Namely, some methods are missing and require calling .bridgeToObjectiveC() to get the NSString version. Using that type instead will probably conform to what NSCoder is expecting, though that difference should not be so.
I didn't actually test this claim since I'm not on my dev machine. But that's my gut instinct. Try it and see what happens! If nothing changes, try switching the order of how you're setting the vars and see if it's a problem related to the name field or simply the first line of the init function.

Answer 2

Below code working is swift for save retrieve NSCoding value in UserDefaults
import UIKit
import Foundation
class ViewController: UIViewController {
var employees: Employees?
let static_key = "nscdeing_data_saved"
override func viewDidLoad() {
super.viewDidLoad()
var request = URLRequest(url: URL(string: "http://dummy.restapiexample.com/api/v1/employees")!, cachePolicy: .returnCacheDataElseLoad, timeoutInterval: 60)
request.httpMethod = "GET"
URLSession.shared.dataTask(with: request) { (data, response, error) in
if let status = (response as? HTTPURLResponse)?.statusCode, status == 200, let data = data{
do {
guard let dic = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:Any] else { return }
self.employees = Employees.init(fromDictionary: dic)
let archiveData = try NSKeyedArchiver.archivedData(withRootObject: self.employees as Any, requiringSecureCoding: true)
UserDefaults.standard.set(archiveData, forKey: self.static_key)
} catch let error {
fatalError(error.localizedDescription)
}
}
}.resume()
}
#IBAction func printAction(_ sender: Any) {
if let data = UserDefaults.standard.data(forKey: static_key){
do {
let value = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data)
print(value as Any)
} catch let error {
fatalError(error.localizedDescription)
}
}
}
}
class Employees : NSObject, NSCoding, NSSecureCoding{
static var supportsSecureCoding: Bool{
return true
}
var data : [Datum]!
var status : String!
/**
* Instantiate the instance using the passed dictionary values to set the properties values
*/
init(fromDictionary dictionary: [String:Any]){
status = dictionary["status"] as? String
data = [Datum]()
if let dataArray = dictionary["data"] as? [[String:Any]]{
for dic in dataArray{
let value = Datum(fromDictionary: dic)
data.append(value)
}
}
}
/**
* Returns all the available property values in the form of [String:Any] object where the key is the approperiate json key and the value is the value of the corresponding property
*/
func toDictionary() -> [String:Any]{
var dictionary = [String:Any]()
if status != nil{
dictionary["status"] = status
}
if data != nil{
var dictionaryElements = [[String:Any]]()
for dataElement in data {
dictionaryElements.append(dataElement.toDictionary())
}
dictionary["data"] = dictionaryElements
}
return dictionary
}
/**
* NSCoding required initializer.
* Fills the data from the passed decoder
*/
#objc required init(coder aDecoder: NSCoder){
data = aDecoder.decodeObject(forKey: "data") as? [Datum]
status = aDecoder.decodeObject(forKey: "status") as? String
}
/**
* NSCoding required method.
* Encodes mode properties into the decoder
*/
#objc func encode(with aCoder: NSCoder){
if data != nil{
aCoder.encode(data, forKey: "data")
}
if status != nil{
aCoder.encode(status, forKey: "status")
}
}
}
class Datum : NSObject, NSCoding, NSSecureCoding{
static var supportsSecureCoding: Bool{
return true
}
var employeeAge : String!
var employeeName : String!
var employeeSalary : String!
var id : String!
var profileImage : String!
/**
* Instantiate the instance using the passed dictionary values to set the properties values
*/
init(fromDictionary dictionary: [String:Any]){
employeeAge = dictionary["employee_age"] as? String
employeeName = dictionary["employee_name"] as? String
employeeSalary = dictionary["employee_salary"] as? String
id = dictionary["id"] as? String
profileImage = dictionary["profile_image"] as? String
}
/**
* Returns all the available property values in the form of [String:Any] object where the key is the approperiate json key and the value is the value of the corresponding property
*/
func toDictionary() -> [String:Any]{
var dictionary = [String:Any]()
if employeeAge != nil{
dictionary["employee_age"] = employeeAge
}
if employeeName != nil{
dictionary["employee_name"] = employeeName
}
if employeeSalary != nil{
dictionary["employee_salary"] = employeeSalary
}
if id != nil{
dictionary["id"] = id
}
if profileImage != nil{
dictionary["profile_image"] = profileImage
}
return dictionary
}
/**
* NSCoding required initializer.
* Fills the data from the passed decoder
*/
#objc required init(coder aDecoder: NSCoder){
employeeAge = aDecoder.decodeObject(forKey: "employee_age") as? String
employeeName = aDecoder.decodeObject(forKey: "employee_name") as? String
employeeSalary = aDecoder.decodeObject(forKey: "employee_salary") as? String
id = aDecoder.decodeObject(forKey: "id") as? String
profileImage = aDecoder.decodeObject(forKey: "profile_image") as? String
}
/**
* NSCoding required method.
* Encodes mode properties into the decoder
*/
#objc func encode(with aCoder: NSCoder){
if employeeAge != nil{
aCoder.encode(employeeAge, forKey: "employee_age")
}
if employeeName != nil{
aCoder.encode(employeeName, forKey: "employee_name")
}
if employeeSalary != nil{
aCoder.encode(employeeSalary, forKey: "employee_salary")
}
if id != nil{
aCoder.encode(id, forKey: "id")
}
if profileImage != nil{
aCoder.encode(profileImage, forKey: "profile_image")
}
}
}