How to retain the values of an array

Question

I have two view controllers. The first one has a segue to another view controller. What I want for the latter view controller is to add items coming from a text field then save it in an array through a button click. Then this array will be saved using NSUserDefaults.

On the code below, I can store items in my array successfully. This array is also saved using NSUserDefaults. Yet, when I get back to my first view controller, and then proceed again to my 2nd view controller to add new items on my array, the items I stored earlier were gone. The newly added items were the only ones saved.

Advice please :)

in my .h file

@interface AddCardViewController : UIViewController <UITextFieldDelegate>

@property (strong, nonatomic) IBOutlet UITextField *cardNameTextField;

@end

in my .m file

@interface AddCardViewController ()

@property (nonatomic, strong)NSMutableArray *nameOfCards;

@end


@implementation AddCardViewController 

@synthesize cardNameTextField = _cardNameTextField;

@synthesize nameOfCards = _nameOfCards;


// setting my array
- (NSMutableArray *)nameOfCards 
{
    if (!_nameOfCards) _nameOfCards = [[NSMutableArray alloc] init];

    return _nameOfCards;
}

- (void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];

    self.cardNameTextField.delegate = self;
}


- (BOOL) textFieldShouldReturn:(UITextField *)textField{

    [self.cardNameTextField resignFirstResponder];

    return YES;
}

- (void)viewDidLoad
{
    //getting the data saved

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    NSMutableArray *cardName = [defaults objectForKey:@"cardName"];

    NSLog(@"contents of my array %@", cardName);

    [super viewDidLoad];

}

- (IBAction)addNewCard:(id)sender {
    [self.nameOfCards addObject:self.cardNameTextField.text];
    NSLog(@"contents :%@", _nameOfCards);


    // this is how to save the data

    NSMutableArray *cardName = _nameOfCards;

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    [defaults setObject:cardName forKey:@"cardName"];

    [defaults synchronize];

    NSLog(@"data saved");

}


@end

An array of objects cannot be directly "saved". The array contains just pointers (addresses). If you save and reload them, they'll have ambiguous meaning. You need to serialize it. Reconstruct a string based on the array or something. — He Shiming, Apr 09 '12 at 06:15
for saving array of values, better to use plist instead of NSUserDefaults.. — vishy, Apr 09 '12 at 06:24
@HeShiming Thanks for the advice. How do I serialize the array? I'm new to this programming language so I didn't quite get that. — Hans, Apr 09 '12 at 06:25

score 2 · Answer 1 · answered Apr 10 '12 at 04:11

Objects retrieved from NSUserDefaults are always immutable, even if you set a mutable object for a key. You can think of it as NSUserDefaults making a copy.

If you need a mutable object based on what is stored in NSUserDefaults, make a mutable copy. For example:

NSMutableArray *cardName = [[[defaults objectForKey:@"cardName"] mutableCopy] autorelease];

The iOSDev · Answer 2 · 2012-04-10T06:03:11.477

0

as the code given above shows that you just set the newly created cardname object i think you have to first fetch all data from nsuserdefaluts and add them to your _nameOfCards array and then add your new objects in addNewCard:(id)sender method like

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

NSMutableArray *cardName = [defaults objectForKey:@"cardName"];
self.nameOfCards = cardName;

[self.nameOfCards addObject:self.cardNameTextField.text];

NSMutableArray *finalCardNames = [[NSMutableArray alloc] initWithArray:self.nameOfCards copyItems:YES];

[defaults setObject:finalCardNames forKey:@"cardName"];

[defaults synchronize];

i think this will solve your problem try it have nice day

edited Apr 10 '12 at 06:03

answered Apr 09 '12 at 06:29

The iOSDev

5,237
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The code you suggested adds a new item in the saved array. However, the next moment I add a new item again, the app crashes and gives this notification. *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFArray insertObject:atIndex:]: mutating method sent to immutable object' – Hans Apr 10 '12 at 01:45

score 0 · Answer 3 · edited May 23 '17 at 12:11

0

Try using a singleton, instead. See my answer here: https://stackoverflow.com/a/10093449/542400 but make it an NSArray instead of a dictionary.

edited May 23 '17 at 12:11

Community

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answered Apr 10 '12 at 18:01

AMayes

1,767
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score 0 · Answer 4 · answered Jan 24 '13 at 07:37

0

it is better for you to use NSMutableArray than NSArray since you can edit, add and delete elements from NSMutableArray. Hope this helps.

answered Jan 24 '13 at 07:37

note-knotz

173
2
8

How to retain the values of an array

4 Answers4