NSMutableArray disappears after app kill or restart using NSKeyedArchiver

I have an app that is storing Task objects (custom class) inside of a NSMutableArray. The Task class conforms to the NSCoding and NSCopying protocols, and I have also implemented the encodeWithCoder and initWithCoder methods.

When the user adds a new task to an NSMutableArray list, I save the array using NSKeyedArchiver. The list populates a UITableView.

The data is being saved, and when I exit the app and reenter, the data is still there. When I use another app for a while and come back, the data is still there. However, when I "kill" the app in the multitasking task manage or restart the device, the data disappears. Here are some important code snippets:

#define kFilename @"epapsTasksFile"

.

- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:kFilename];
}

- (voi开发者_StackOverflowd)viewDidLoad {

    NSString *filePath = [self dataFilePath];
    if([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        self.list = [[NSKeyedUnarchiver unarchiveObjectWithFile:kFilename] retain];
    }
    else {
        self.list = [NSMutableArray arrayWithCapacity:1];
    }

    ...
}

- (void)applicationWillResignActive:(NSNotification *)notification {
    NSMutableArray *updatedList = [[NSMutableArray alloc] initWithArray:self.list];
    [NSKeyedArchiver archiveRootObject:updatedList toFile:kFilename];
}

Why is my app not saving the data when the app is "killed" or the device is restarted? Also, it may be interesting to note that when I restart the iPhone simulator, the data stays in place.

You need to save the data
([NSKeyedArchiver archiveRootObject:updatedList toFile:kFilename]; in applicationWillTerminate delegate method as as well to save it on termination.

EDIT: applicationWillTerminate is not gauranteed in IOS4.0 and above.

Best is to check the return status of archiveRootObject:toFile: and see if the data is stored properly. As you figured it out, it can be case with wrong file path.