custom_user_defaults.md

How to store custom objects in UserDefaults

We can store values in iOS using UserDefault. It supports storing strings, integers, lists etc. But if we need to store custom objects, what should we do?

• Let's say we have a custom object called NotificationModel. It is important to note that we need to extend the custom object with Codable to ensure that the custom object is encodable or decodable.

public class NotificationModel : NSObject, Codable {
    
    private var _title: String = ""
    var title: String {
        set { _title = title }
        get { return _title }
    }
    
    
    private var _body: String = ""
    var body: String {
        set { _body = body }
        get { return _body }
    }
    
    
    private var _timeStamp: String = ""
    var timeStamp: String {
        set { _timeStamp = timeStamp }
        get { return _timeStamp }
    }
    
    init(info: Dictionary<String, AnyObject>) {
        self._title = info["title"] as! String
        self._body = info["body"] as! String
        self._timeStamp = String(Date().toMillis())
    }
    
    required public init(coder aDecoder: NSCoder) {
        self._title = aDecoder.decodeObject(forKey: "title") as! String
        self._body = aDecoder.decodeObject(forKey: "body") as! String
        self._timeStamp = aDecoder.decodeObject(forKey: "timeStamp") as! String
    }
    
    public func encode(with aCoder: NSCoder) {
        aCoder.encode(_title, forKey: "title")
        aCoder.encode(_body, forKey: "body")
        aCoder.encode(_timeStamp, forKey: "timeStamp")
    }
}

• We can initialize the custom object class like this:

  let data: Dictionary<String, AnyObject> = ["title" : "Anitaa" as AnyObject, "body" : "Test1" as AnyObject, "timeStamp" : "1532683817" as AnyObject]
  let notification: NotificationModel = NotificationModel(info: data)
  

• Now let's store the notification object received from the app in UserDefaults. We need to use JSONEncoder to encode the object first:

  let notification: NotificationModel = NotificationModel(info: data)
  
  if let encoded = try? JSONEncoder().encode(notification) {
      UserDefaults.standard.set(encoded, forKey: "notification")
  }
  

• Now let's get the list of notifications from UserDefault. We use JSONDecoder to decode the object first:

  if let notifications = UserDefaults.standard.data(forKey: "notification"),
    let notifications = try? JSONDecoder().decode(Notification.self, from: notifications) {
  
    dump(notification)
  }