Attempt to set a non-property-list object as an NSUserDefaults

> Swift 5: The **Codable** protocol can be used instead of **NSKeyedArchiever**.

struct User: Codable {
let id: String
let mail: String
let fullName: String
}

The **Pref** struct is custom wrapper around the UserDefaults standard object.

struct Pref {
static let keyUser = "Pref.User"
static var user: User? {
get {
if let data = UserDefaults.standard.object(forKey: keyUser) as? Data {
do {
return try JSONDecoder().decode(User.self, from: data)
} catch {
print("Error while decoding user data")
}
}
return nil
}
set {
if let newValue = newValue {
do {
let data = try JSONEncoder().encode(newValue)
UserDefaults.standard.set(data, forKey: keyUser)
} catch {
print("Error while encoding user data")
}
} else {
UserDefaults.standard.removeObject(forKey: keyUser)
}
}
}
}

So you can use it this way:

Pref.user?.name = "John"

if let user = Pref.user {...

**Swift** with `@propertyWrapper`

Save `Codable` object to `UserDefault`


@propertyWrapper
struct UserDefault<T: Codable> {
let key: String
let defaultValue: T

init(_ key: String, defaultValue: T) {
self.key = key
self.defaultValue = defaultValue
}

var wrappedValue: T {
get {

if let data = UserDefaults.standard.object(forKey: key) as? Data,
let user = try? JSONDecoder().decode(T.self, from: data) {
return user

}

return defaultValue
}
set {
if let encoded = try? JSONEncoder().encode(newValue) {
UserDefaults.standard.set(encoded, forKey: key)
}
}
}
}




enum GlobalSettings {

@UserDefault("user", defaultValue: User(name:"",pass:"")) static var user: User
}




Example User model confirm Codable

struct User:Codable {
let name:String
let pass:String
}

**How to use it**


//Set value
GlobalSettings.user = User(name: "Ahmed", pass: "Ahmed")

//GetValue
print(GlobalSettings.user)

I ran into this and eventually figured out it was because I was trying to use `NSNumber` as dictionary keys, and property lists only allow strings as keys. The documentation for [`setObject:forKey:`](

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) doesn't mention this limitation, but the [About Property Lists](

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) page that it links to does:

> By convention, each Cocoa and Core Foundation object listed in Table 2-1 is called a property-list object. Conceptually, you can think of “property list” as being an abstract superclass of all these classes. If you receive a property list object from some method or function, you know that it must be an instance of one of these types, but a priori you may not know which type. If a property-list object is a container (that is, an array or dictionary), all objects contained within it must also be property-list objects. If an array or dictionary contains objects that are not property-list objects, then you cannot save and restore the hierarchy of data using the various property-list methods and functions. And although NSDictionary and CFDictionary objects allow their keys to be objects of any type, <b>if the keys are not string objects, the collections are not property-list objects.</b>

(Emphasis mine)