Question

I have a class called “Timestamp”. This class contains a static NSDate variable which is initialized the FIRST time using NSUserDefaults the app opens. This date is turned into a string which is used later. This is how I first configure date:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *string = [defaults objectForKey:@"timestampCheck"];

if (!string) { 

    Timestamp *tstamp = [[Timestamp alloc] init];
    [tstamp setSingleTimeStamp : [NSDate date]];
    [tstamp release];

    [defaults setObject:@"notFirst" forKey:@"timestampCheck"];
    [defaults synchronize];

} else {

    Timestamp *ti = [[Timestamp alloc] init];
    [ti initializeTimestamp];
    [ti release];

}

initializeTimestamp 

method is just retrieving the timestamp from the defaults. Which is set in a method called:synchronizeTimestamp

That method is called when the app enters background state.

The Timestamp class looks like this:

    - (void)setSingleTimeStamp:(NSDate *)dateProvided {

    date = dateProvided;
    [date retain];
}

- (void)synchronizeTimestamp {

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    [defaults setObject:date forKey:@"timestampDate"];

    [defaults synchronize];

}

- (void)initializeTimestamp {

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    date = [defaults objectForKey:@"timestampDate"];

}

- (NSString *)dateStringContainer {


    NSDate *tempDate = date; 

    unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *components = [calendar components:units fromDate:tempDate];

    NSInteger year = [components year];
    NSInteger month = [components month];
    NSInteger day = [components day];

    return [NSString stringWithFormat:@"%i - %i - %i", day, month, year]; 

}

A label’s text in a separate view controller is set to dateStringContainer. Of course when I delete and build my app it shows the right date. But when I quit the app and delete from the multitasking bar the label text is:

1 - 1 - 2001

And date is nil, after some NSLog's

UPDATE:

Ok so basically, the date is working the first time the app opens ( I have to delete the app every single time to do this ), when my app is plugged in. But when I go back to it after removing it from the multitasking bar, the date is incorrect. This means that there is something wrong with my NSUserDefaults code right? Just guessing…

EDIT:

I have noticed that my synchronizeTimestamp method isn’t called. But that may be because I am stopping the app on Xcode, does stopping that app on Xcode turn it into background mode?

Answer 1

You will have to retain the following

date = [defaults objectForKey:@"timestampDate"];

wich should be

date = [[defaults objectForKey:@"timestampDate"] retain];

Since the defaults will return an autoreleased object,
I dont know if this will fix all your problems, but it is certainly a bug