Loading data back from NSUserDefaults

Question

In ViewController3 the user can save some text via button click to the NSUserDefaults (to use it elsewhere). In the same ViewController there is also a tableView (used to delete specific items from NSUserDefaults)

So I have to load the data back with:

override func viewDidLoad() {
    super.viewDidLoad()

    var exercisescopy = NSMutableArray(array: exercises)

    var userDefaults:NSUserDefaults = NSUserDefaults.standardUserDefaults()

    var exercisesListFromUserDefaults:NSMutableArray? = userDefaults.objectForKey("exercisesList") as? NSMutableArray

    if ((exercisesListFromUserDefaults) != nil){
        exercises = exercisesListFromUserDefaults!
    }
    self.tableView.reloadData()

}

so that the data is there when you get to the third ViewController but how to get the data right back after saving a new element to NSUserDefaults? So that it is displayed in the tableView right now?

The table view is in the same controller as is saving the data to user defaults? — Wain, Feb 01 '15 at 10:17

score 0 · Accepted Answer · edited May 23 '17 at 12:12

You can use NSNotificationCenter to observe changes in NSUserDefaults.

This answer describes it well.

For swift it is:

NSNotificationCenter.defaultCenter().addObserver(self, "reloadMyData:", NSUserDefaultsDidChangeNotification, nil)

Where reloadMyData: is your function to trigger table reloading.

Don't forget to strip the observer in deinit as in:

deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

score 0 · Answer 2 · answered Feb 01 '15 at 11:54

You really don't wanna do this, Using the NSUserDefault for passing Data. NSNotification center is cool about that as @Burton suggested. If your data is really big you can use CoreData. If you really wanna do this that you intend here is how ...

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];  
NSString *firstName = [defaults objectForKey:@"firstName"];
NSString *lastName = [defaults objectForKey:@"lastname"];

Here assummed that firstname & lastname were saved preiviously.

Loading data back from NSUserDefaults

2 Answers2