How can I store an array of custom objects (Goals) - ios

Question

How can I store an array of objects of type Goal which I have created in NSUserDefaults? (in swift)
Here is the code:
func saveGoalList ( newGoalList : [Goal] ){
let updatedGoalList = newGoalList;
NSUserDefaults.standardUserDefaults().setObject(updatedGoalList, forKey: "GoalList")
NSUserDefaults.standardUserDefaults().synchronize()
}
class GoalsViewController: MainPageContentViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet var tableView: GoalsTableView!
var cell = GoalTableViewCell()
var goalsArray : Array<Goal> = [] //
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.delegate = self
self.tableView.dataSource = self
if var storedGoalList: [Goal] = NSUserDefaults.standardUserDefaults().objectForKey("GoalList") as? [Goal]{
goalsArray = storedGoalList;
}
var goal = Goal(title: "Walk the Dog")
goalsArray.append(goal)
saveGoalList(goalsArray)
self.tableView?.reloadData()
tableView.estimatedRowHeight = 44.0
tableView.rowHeight = UITableViewAutomaticDimension
self.xpnotificationView.alpha = 0.0
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return goalsArray.count //to ensure there is always an extra cell to fill in.
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { //recreate the cell and try using it.
cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as GoalTableViewCell
cell.goalTextField.text = goalsArray[indexPath.row].title as String!
cell.checkmarkImageView.visible = goalsArray[indexPath.row].checkmarked as Bool!
if (cell.checkmarkImageView.visible == true) {
cell.blackLineView.alpha = 1.0
} else {
cell.blackLineView.alpha = 0.0
}
return cell
}
}
I understand that there are only certain data types that work with NSUserDefaults. Could anyone help me understand how I could do that?
Edit: Right now Goal inherits from NSObject.

Answer 1

I am posting code from a learning project I did to store objects using NSCoding. Fully functional and ready to use. A math game that was storing game variables, etc.
//********This class creates the object and properties to store********
import Foundation
class ButtonStates: NSObject {
var sign: String = "+"
var level: Int = 1
var problems: Int = 10
var time: Int = 30
var skipWrongAnswers = true
func encodeWithCoder(aCoder: NSCoder!) {
aCoder.encodeObject(sign, forKey: "sign")
aCoder.encodeInteger(level, forKey: "level")
aCoder.encodeInteger(problems, forKey: "problems")
aCoder.encodeInteger(time, forKey: "time")
aCoder.encodeBool(skipWrongAnswers, forKey: "skipWrongAnswers")
}
init(coder aDecoder: NSCoder!) {
sign = aDecoder.decodeObjectForKey("sign") as String
level = aDecoder.decodeIntegerForKey("level")
problems = aDecoder.decodeIntegerForKey("problems")
time = aDecoder.decodeIntegerForKey("time")
skipWrongAnswers = aDecoder.decodeBoolForKey("skipWrongAnswers")
}
override init() {
}
}
//********Here is the data archiving and retrieving class********
class ArchiveButtonStates:NSObject {
var documentDirectories:NSArray = []
var documentDirectory:String = ""
var path:String = ""
func ArchiveButtons(#buttonStates: ButtonStates) {
documentDirectories = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
documentDirectory = documentDirectories.objectAtIndex(0) as String
path = documentDirectory.stringByAppendingPathComponent("buttonStates.archive")
if NSKeyedArchiver.archiveRootObject(buttonStates, toFile: path) {
//println("Success writing to file!")
} else {
println("Unable to write to file!")
}
}
func RetrieveButtons() -> NSObject {
var dataToRetrieve = ButtonStates()
documentDirectories = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
documentDirectory = documentDirectories.objectAtIndex(0) as String
path = documentDirectory.stringByAppendingPathComponent("buttonStates.archive")
if let dataToRetrieve2 = NSKeyedUnarchiver.unarchiveObjectWithFile(path) as? ButtonStates {
dataToRetrieve = dataToRetrieve2 as ButtonStates
}
return(dataToRetrieve)
}
}
the following is in my ViewController where the game is played. Only showing the relevant code for retrieving and storing objects
class mathGame: UIViewController {
var buttonStates = ButtonStates()
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
//set inital view
//retrieving a stored object & placing property into local class variables
buttonStates = ArchiveButtonStates().RetrieveButtons() as ButtonStates
gameData.sign = buttonStates.sign
gameData.level = buttonStates.level
gameData.problems = buttonStates.problems
gameData.time = buttonStates.time
}
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(animated)
//storing the object
ArchiveButtonStates().ArchiveButtons(buttonStates: buttonStates)
}
}

Answer 2

You need your class to adopt the NSCoding protocol and encode and decode itself, like this:
https://github.com/mattneub/Programming-iOS-Book-Examples/blob/master/bk2ch23p798basicFileOperations/ch36p1053basicFileOperations/Person.swift
Now you can transform an instance of your class into an NSData by calling NSKeyedArchiver.archivedDataWithRootObject: - and an NSData can go into NSUserDefaults.
This also means that an NSArray of instances of your class can be transformed into an NSData by the same means.

Answer 3

For Swift 2.1, your Goal class should look like :
import Foundation
class Goal : NSObject, NSCoding {
var title: String
// designated initializer
init(title: String) {
self.title = title
super.init() // call NSObject's init method
}
// MARK: - comply wiht NSCoding protocol
func encodeWithCoder(aCoder: NSCoder) {
aCoder.encodeObject(title, forKey: "GoalTitle")
}
required convenience init?(coder aDecoder: NSCoder) {
// decoding could fail, for example when no Blog was saved before calling decode
guard let unarchivedGoalTitle = aDecoder.decodeObjectForKey("GoalTitle") as? String
else {
// option 1 : return an default Blog
self.init(title: "unknown")
return
// option 2 : return nil, and handle the error at higher level
}
// convenience init must call the designated init
self.init(title: unarchivedGoalTitle)
}
}
and you should use it in your view controller like I did in this test code :
// create an array with test data
let goal1 = Goal(title: "first goal")
let goal2 = Goal(title: "second goal")
let goalArray = [goal1, goal2]
// first convert the array of custom Goal objects to a NSData blob, as NSUserDefaults cannot handle arrays of custom objects directly
let dataBlob = NSKeyedArchiver.archivedDataWithRootObject(goalArray)
// this NSData object can now be stored in the user defaults
NSUserDefaults.standardUserDefaults().setObject(dataBlob, forKey: "myGoals")
// sync to make sure they are saved before we retreive anytying
NSUserDefaults.standardUserDefaults().synchronize()
// now read back
if let decodedNSDataBlob = NSUserDefaults.standardUserDefaults().objectForKey("myGoals") as? NSData {
if let loadedGoalsArray = NSKeyedUnarchiver.unarchiveObjectWithData(decodedNSDataBlob) as? [Goal] {
for goal in loadedGoalsArray {
print("goal : \(goal.title)")
}
}
}
As a final remark : it would be easier to use NSKeyedArchiver instead of NSUserDefaults, and store your array of custom objects directly to a file. You can read more about the difference between both methods in another answer I posted here.