Added property to struct which in Swift - invalidates existing objects - swift

Question

I am new to Swift, but have some basic experience with Objective-C programming, and Swift seems much simpler.
However, I can't quite understand the struct thing. I followed a tutorial on how to use Firebase Realtime Database, and this tutorial were using a model to store the data.
But when I modified the struct with additional properties, the previously saved entries in the database is not showing up. I think it's because the model doesn't recognize the object in the database because it has different properties, but how can I make a property optional? So that old entries in the database with different structure (missing properties) are still valid and showing up?
Here is the model. The new property added is all the references to the description.
import Foundation
import Firebase
struct InsuranceItem {
let ref: DatabaseReference?
let key: String
let name: String
let timestamp: Int
let itemValue: Int
let description: String?
let userId: String?
init(name: String, timestamp: Int, itemValue: Int = 0, description: String = "", userId: String, key: String = "") {
self.ref = nil
self.key = key
self.name = name
self.timestamp = Int(Date().timeIntervalSince1970)
self.itemValue = itemValue
self.description = description
self.userId = userId
}
init?(snapshot: DataSnapshot) {
guard
let value = snapshot.value as? [String: AnyObject],
let name = value["name"] as? String,
let timestamp = value["timestamp"] as? Int,
let itemValue = value["itemValue"] as? Int,
let description = value["description"] as? String,
let userId = value["userId"] as? String else { return nil }
self.ref = snapshot.ref
self.key = snapshot.key
self.name = name
self.timestamp = timestamp
self.itemValue = itemValue
self.description = description
self.userId = userId
}
func toAnyObject() -> Any {
return [
"name": name,
"timestamp": timestamp,
"itemValue": itemValue,
"description": description!,
"userId": userId!
]
}
}

Answer 1

The problematic bit is your failable init, init?(snapshot: DataSnapshot). You fail the init even if an Optional property is missing, which is incorrect. You should only include the non-Optional properties in your guard statement, all others should simply be assigned with the optional casted value.
init?(snapshot: DataSnapshot) {
guard
let value = snapshot.value as? [String: Any],
let name = value["name"] as? String,
let timestamp = value["timestamp"] as? Int,
let itemValue = value["itemValue"] as? Int else { return nil }
self.ref = snapshot.ref
self.key = snapshot.key
self.name = name
self.timestamp = timestamp
self.itemValue = itemValue
// Optional properties
let description = value["description"] as? String
let userId = value["userId"] as? String
self.description = description
self.userId = userId
}
Unrelated to your question, but your toAnyObject function is unsafe, since you are force-unwrapping Optional values. Simply keep them as Optionals without any unwrapping and add as Any to silence the warning for implicit coersion.
func toAnyObject() -> Any {
return [
"name": name,
"timestamp": timestamp,
"itemValue": itemValue,
"description": description as Any,
"userId": userId as Any
]
}