Swift 3 saving and retrieving custom object from userDefaults

Swift 4 or later

You can once again save/test your values in a Playground

---

UserDefaults need to be tested in a real project. Note: No need to force synchronize. If you want to test the coding/decoding in a playground you can save the data to a plist file in the document directory using the keyed archiver. You need also to fix some issues in your class:

class Person: NSObject, NSCoding {
    let name: String
    let age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "name") as? String ?? ""
        self.age = decoder.decodeInteger(forKey: "age")
    }
    
    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
        coder.encode(age, forKey: "age")
    }
}

Testing:

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setting a value for a key
        do {
            let newPerson = Person(name: "Joe", age: 10)
            var people = [Person]()
            people.append(newPerson)
            let encodedData = try NSKeyedArchiver.archivedData(withRootObject: people, requiringSecureCoding: false)
            UserDefaults.standard.set(encodedData, forKey: "people")
                
        } catch {
            print(error)
        }
        
        // retrieving a value for a key
        do {
            if let data = UserDefaults.standard.data(forKey: "people"),
                let myPeopleList = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? [Person] {
                myPeopleList.forEach({print( $0.name, $0.age)})  // Joe 10
            } else {
                print("There is an issue")
            }
        } catch {
            print(error)
        }
    }
}

let age = aDecoder.decodeObject(forKey: "age") as! Int

This has been changed for Swift 3; this no longer works for value types. The correct syntax is now:

let age = aDecoder.decodeInteger(forKey: "age")

There are associated decode...() functions for various different types:

let myBool = aDecoder.decodeBoolean(forKey: "myStoredBool")
let myFloat = aDecoder.decodeFloat(forKey: "myStoredFloat")

Edit: Full list of all possible decodeXXX functions in Swift 3

Edit:

Another important note: If you have previously saved data that was encoded with an older version of Swift, those values must be decoded using decodeObject(), however once you re-encode the data using encode(...) it can no longer be decoded with decodeObject() if it's a value type. Therefore Markus Wyss's answer will allow you to handle the case where the data was encoded using either Swift version:

self.age = aDecoder.decodeObject(forKey: "age") as? Int ?? aDecoder.decodeInteger(forKey: "age")

In Swift 4:

You can use Codable to save and retrieve custom object from the Userdefaults. If you're doing it frequently then you can add as extension and use it like below.

extension UserDefaults {

   func save<T:Encodable>(customObject object: T, inKey key: String) {
       let encoder = JSONEncoder()
       if let encoded = try? encoder.encode(object) {
           self.set(encoded, forKey: key)
       }
   }

   func retrieve<T:Decodable>(object type:T.Type, fromKey key: String) -> T? {
       if let data = self.data(forKey: key) {
           let decoder = JSONDecoder()
           if let object = try? decoder.decode(type, from: data) {
               return object
           }else {
               print("Couldnt decode object")
               return nil
           }
       }else {
           print("Couldnt find key")
           return nil
       }
   }

}

Your Class must follow Codable. Its just a typealias for both Encodable & Decodable Protocol.

class UpdateProfile: Codable {
  //Your stuffs
}

Usage:

let updateProfile = UpdateProfile()

//To save the object
UserDefaults.standard.save(customObject: updateProfile, inKey: "YourKey")

//To retrieve the saved object
let obj = UserDefaults.standard.retrieve(object: UpdateProfile.self, fromKey: "YourKey")

For more Encoding and Decoding Custom types, Please go through the Apple's documentation.