How to archive and unarchive custom objects in Swift? Or how to save custom object to NSUserDefaults in Swift?

Question

I have a class

class Player {

    var name = \"\"

    func encodeWithCoder(encoder: NSCoder) {
        encoder.encodeObject(name)
    }

    func initWith         


        

Answer 1

I have a class

    class Player {
        var name = ""
        init(name: String) {
            self.name = name
        }
    }

and i want to serialise it and save to user defaults.

In Swift 4 / iOS 11, there's a whole new way to do this. It has the advantage that any Swift object can use it — not just classes, but also structs and enums.

You'll notice that I've omitted your NSCoding-related methods, because you won't need them for this purpose. You can adopt NSCoding here, as you know; but you don't have to. (And a struct or enum cannot adopt NSCoding at all.)

You start by declaring your class as adopting the Codable protocol:

class Player : Codable {
    var name = ""
    init(name: String) {
        self.name = name
    }
}

It then becomes a simple matter to serialize it into a Data object (NSData) which can be stored in UserDefaults. The very simplest way is to use a property list as an intermediary:

let player = Player(name:"matt")
try? UserDefaults.standard.set(PropertyListEncoder().encode(player), 
    forKey:"player")

If you use that approach, let's now prove that you can pull the same Player back out of UserDefaults:

if let data = UserDefaults.standard.object(forKey:"player") as? Data {
    if let p = try? PropertyListDecoder().decode(Player.self, from: data) {
        print(p.name) // "matt"
    }
}

If you'd rather pass through an NSKeyedArchiver / NSKeyedUnarchiver, you can do that instead. Indeed, there are some situations where you'll have to do so: you'll be presented with an NSCoder, and you'll need to encode your Codable object inside it. In a recent beta, Xcode 9 introduced a way to do that too. For example, if you're encoding, you cast the NSCoder down to an NSKeyedArchiver and call encodeEncodable.