Mirrored user defaults

import Foundation
import CoreData
import CloudKit

// https://github.com/macmade/user-defaults/blob/master/swift/Preferences.swift

/*******************************************************************************
 * The MIT License (MIT)
 *
 * Copyright (c) 2017 Jean-David Gadina - www.xs-labs.com
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 ******************************************************************************/

@objc public class UserDevicePreferences: NSObject
{
    
    // add default value like this: @objc public dynamic var fontSize:  CGFloat = 0
    
    @objc public dynamic var lastPlanAddedTo: UUID?
    @objc public dynamic var persistentHistoryTokeniOS: NSPersistentHistoryToken?
    @objc public dynamic var persistentHistoryTokeniOSCloudContext: NSPersistentHistoryToken?
    @objc public dynamic var cloudPlacesZoneSubscription: CKDatabaseSubscription?
    @objc public dynamic var cloudDatabaseSubscription: CKRecordZoneSubscription?
    
    @objc public static let shared = UserDevicePreferences()
    
    private override init() {
        super.init()

        // Register defaults something like this:
//        if let path = Bundle.main.path( forResource: "Defaults", ofType: "plist" ) {
//            UserDefaults.standard.register( defaults: NSDictionary( contentsOfFile: path ) as? [ String : Any ] ?? [ : ] )
//        }
        
        for c in Mirror(reflecting: self).children {
            guard let key = c.label else {
                continue
            }
            
            if let value = UserDefaults.shared.object(forKey: key ) {
                self.setValue(value, forKey: key )
            }
            
            self.addObserver(self, forKeyPath: key, options: .new, context: nil )
        }
    }
    
    deinit {
        for c in Mirror( reflecting: self ).children {
            guard let key = c.label else {
                continue
            }
            self.removeObserver(self, forKeyPath: key )
        }
    }
    
    public override func observeValue(forKeyPath keyPath: String?,
                                      of object: Any?,
                                      change: [NSKeyValueChangeKey : Any]?,
                                      context: UnsafeMutableRawPointer?) {
        var found = false
        for c in Mirror(reflecting: self).children {
            guard let key = c.label else {
                continue
            }
            
            if(key == keyPath) {
                UserDefaults.shared.set(change?[NSKeyValueChangeKey.newKey], forKey: key)
                found = true
                break
            }
        }
        
        if(found == false) {
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        }
    }
}