Swift saving and retrieving custom object from UserDefaults

Question

I have this in Playground using Swift 3, Xcode 8.0:

import Foundation class Person: NSObject, NSCoding {     var name: String     var age: Int     init(name: String, age: Int) {         self.name = name         self.age = age     }     required convenience init(coder aDecoder: NSCoder) {         let name = aDecoder.decodeObject(forKey: "name") as! String         let age = aDecoder.decodeObject(forKey: "age") as! Int         self.init(             name: name,             age: age         )     }     func encode(with aCoder: NSCoder) {         aCoder.encode(name, forKey: "name")         aCoder.encode(age, forKey: "age")     } } 

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create array of Person

let newPerson = Person(name: "Joe", age: 10) var people = [Person]() people.append(newPerson) 

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encode the array

let encodedData = NSKeyedArchiver.archivedData(withRootObject: people) print("encodedData: \(encodedData))") 

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save to userDefaults

let userDefaults: UserDefaults = UserDefaults.standard() userDefaults.set(encodedData, forKey: "people") userDefaults.synchronize() 

---

check

print("saved object: \(userDefaults.object(forKey: "people"))") 

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retreive from userDefaults

if let data = userDefaults.object(forKey: "people") {     let myPeopleList = NSKeyedUnarchiver.unarchiveObject(with: data as! Data)     print("myPeopleList: \(myPeopleList)") }else{     print("There is an issue") } 

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just check the archived data

if let myPeopleList = NSKeyedUnarchiver.unarchiveObject(with: encodedData){    print("myPeopleList: \(myPeopleList)") }else{    print("There is an issue") } 

I'm not able to correctly save the data object to userDefaults, and in addition, the check at the bottom creates the error:

Fatal error: Unexpectedly found nil while unwrapping an Optional value

The "check" line also shows the saved object is nil. Is this an error in my object's NSCoder?

Answer 1

Swift 4 or later

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

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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:

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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")     } } 

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Testing:

class ViewController: UIViewController {     override func viewDidLoad() {         super.viewDidLoad()          do {             // setting a value for a key             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")             // retrieving a value for a key             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             }                             } catch {             print(error)         }              } } 

Answer 2

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")