NSUserDefaults unable to save and read my custom objects

Question

I have a class Notification that implements the NSCoding protocol.
I have an array of notifications.I am trying to save the notifications with NSUserDefaults.In my app delegate notifications is a NSMutableArray that contains the Notification objects.That's my app delegate:

+ (void) initialize
{
    NSUserDefaults* defaults=[NSUserDefaults standardUserDefaults];
    [defaults registerDefaults: [NSDictionary dictionaryWithObject: [NSKeyedArchiver archivedDataWithRootObject: [NSArray array]] forKey: @"notificationsData"]];
}


- (id) init
{
    self=[super init];
    if(self)
    {
        NSUserDefaults* defaults=[NSUserDefaults standardUserDefaults];
        NSData* notificationsData=[defaults objectForKey: @"notificationsData"];
        notifications= [[NSKeyedUnarchiver unarchiveObjectWithData: notificationsData]mutableCopy];
    }
    return self;
}

- (void) applicationWillTerminate:(NSNotification *)notification
{
    NSUserDefaults* defaults=[NSUserDefaults standardUserDefaults];
    NSData* notificationsData=[NSKeyedArchiver archivedDataWithRootObject: notifications];
    [defaults setObject: notificationsData forKey: @"notificationsData"];
}

In the Notification class text and title are of type NSString (both readwrite), and date is of type NSDate (also this has readwrite property).This is how I implement the NSCoding protocol:

- (void) encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject: date forKey: @"date"];
    [aCoder encodeObject: title forKey: @"title"];
    [aCoder encodeObject: text forKey: @"text"];
}

- (id) initWithCoder:(NSCoder *)aDecoder
{
    self=[super init];
    if(self)
    {
        date=[aDecoder decodeObjectForKey: @"data"];
        title=[aDecoder decodeObjectForKey: @"title"];
        text=[aDecoder decodeObjectForKey: @"text"];
    }
    return self;
}

So I have these problems:

When the application terminates I get EXC_BAD_ACCESS in the Notification class, when I try to encode text with NSKeyedArchiver;
The notifications aren't saved and the array is always long zero when the application starts.

Update: With more debug I discovered where the application crashes.There is more code to see (I'm using a table view to display the data):

- (NSInteger) numberOfRowsInTableView:(NSTableView *)tableView
{
    return [notifications count];
}

- (id) tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
    // Debug
    id obj=[[notifications objectAtIndex: row] valueForKey: [tableColumn identifier]];
    Class class=[obj class];
    // What you see above is just for debug purposes
    return [[notifications objectAtIndex: row] valueForKey: [tableColumn identifier]];
}

- (void) tableViewSelectionDidChange:(NSNotification *)notification
{
    NSInteger row=[tableView selectedRow];
    if(row >= 0 && row< [notifications count])
        [removeButton setEnabled: YES];
    else
        [removeButton setEnabled: NO];
}

The last method called is this:

- (id) tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row;

Probably the problem is that the data is somehow corrupted and the value returned by this method is not valid.Anyway the app doesn't crash in this method, but after this method.
If I load two objects from user defaults, only one object gets loaded before crashing (so the method gets called once).
However I'm still unable to get the real reason of the crash.

More code:

- (IBAction) addNotification :(id)sender
{
    Notification* notification=[[Notification alloc]init];
    [notification setDate: [datePicker dateValue]];
    [notification setText: [textView string]];
    [notifications addObject: notification];
    [tableView reloadData];
}

- (IBAction)removeNotification:(id)sender
{
    [notifications removeObjectAtIndex: [tableView selectedRow]];
    [tableView reloadData];
}

addNotification and removeNotification are both triggered by buttons.

EDIT: I discovered that I wasn't using ARC, but even if I turn it on the app crashes.

score 2 · Answer 1 · answered Oct 29 '12 at 18:32

2

In the line:

date=[aDecoder decodeObjectForKey: @"data"];

@"data" doesn't match the encoder key. You really want:

date=[aDecoder decodeObjectForKey: @"date"];

answered Oct 29 '12 at 18:32

thelaws

7,991
6
35
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Thanks, now I replaced it.But the program still crashes. – Ramy Al Zuhouri Oct 29 '12 at 18:37
Did you delete the app completely? The old user defaults might still be there. – thelaws Oct 29 '12 at 19:04
I used NSUserDefault's resetStandardUserDefaults method, but the app still crashes. – Ramy Al Zuhouri Oct 29 '12 at 19:28
The code you put in the update looks fine to me. When you debug is obj ever nil? – thelaws Oct 29 '12 at 20:00
obj is not nil, it's a valid object.But if I try to log it's class I get the exception.If I try to debug the initWithCoder method title and date are ok, but look what it says about text: (lldb) print text (NSString *) $3 = 0x000000010050e080 @ – Ramy Al Zuhouri Oct 29 '12 at 20:09
Sorry, I can't see the problem, your add/remvove code looks alright also. Maybe add the exception you're getting when running the app? – thelaws Oct 29 '12 at 20:20
EXC_BAD_ACCESS (code=1, address=0x13) in objc_msgSend, and it shows assembly code. – Ramy Al Zuhouri Oct 29 '12 at 20:24
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/18747/discussion-between-thelaws-and-ramy-al-zuhouri) – thelaws Oct 29 '12 at 20:25

score 1 · Accepted Answer · answered Oct 29 '12 at 17:54

1

You might need to call [NSUserDefaults synchronize] since it will not happen automatically when the application suddenly exits:

- (void) applicationWillTerminate:(NSNotification *)notification
{
    NSUserDefaults* defaults=[NSUserDefaults standardUserDefaults];
    NSData* notificationsData=[NSKeyedArchiver archivedDataWithRootObject: notifications];
    [defaults setObject: notificationsData forKey: @"notificationsData"];
    [defaults synchronize];
}

answered Oct 29 '12 at 17:54

Nathan Villaescusa

17,331
4
53
56

Yes, but it crashes anyway, there's still a problem. – Ramy Al Zuhouri Oct 29 '12 at 18:04
1

What happens if you replace `NSData* notificationsData=[NSKeyedArchiver archivedDataWithRootObject: notifications];` with `NSData* notificationsData=[NSKeyedArchiver archivedDataWithRootObject:@[]];`? – Nathan Villaescusa Oct 29 '12 at 18:21
This case the application runs smoothly, without any exception thrown.But of course since the array is empty, I can't recover the notifications from the previous execution.I doubt that there is something wrong in how I implement the protocol. – Ramy Al Zuhouri Oct 29 '12 at 18:31

score 0 · Answer 3 · answered Oct 30 '12 at 15:27

0

You couldn't guess what was wrong: my bad, I forgot to enable ARC and some objects were released when they shouldn't.

answered Oct 30 '12 at 15:27

Ramy Al Zuhouri

21,580
26
105
187

NSUserDefaults unable to save and read my custom objects

3 Answers3