Cannot figure out why my app crashes when I use NSKeyedArchivers / NSKeyedUnarchivers - iphone

Question

I am developing my first iphone 'Diary' app, which uses custom 'Entry' objects that hold an NSString title, NSString text and NSDate creationDate. When I try to archive an NSMutableArray of Entry objects, and later retrieve them the next time the view loads, the app crashes. I have gone through a bunch of sample codes and examples that use NSKeyedArchivers, but still couldn't figure out why that happens. I am guessing there is a problem with the initialization of the array that holds the entries but not sure...
Here is the code, maybe you could find something that I have persistently overseen..."
//--------- Entry.m---------------
- (id) initWithCoder:(NSCoder *)aDecoder{
if ((self = [super init])) {
self.title = [[aDecoder decodeObjectForKey:#"title"] retain];
self.text = [[aDecoder decodeObjectForKey:#"text"] retain];
self.created = [[aDecoder decodeObjectForKey:#"created"] retain];
}
return self;
}
- (void) encodeWithCoder:(NSCoder *)aCoder{
[aCoder encodeObject:self.title forKey:#"title"];
[aCoder encodeObject:self.text forKey:#"text"];
[aCoder encodeObject:self.created forKey:#"created"];
}
//-------------- Diary View Controller.m
- (NSString *)dataFilePath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return [documentsDirectory stringByAppendingPathComponent:kFilename];
}
- (void) writeDataToArchive {
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]
initForWritingWithMutableData:data];
[archiver encodeObject:self.entriesArray forKey:#"entriesArray"];
[archiver finishEncoding];
BOOL result = [data writeToFile:[self dataFilePath] atomically:YES];
[archiver release];
[data release];
}
- (void)addItem:sender {
int count = [entriesArray count] +1;
NSString *newEntryTitle = [NSString stringWithFormat:#"Entry %d", count];
Entry *anEntry = [[Entry alloc] initWithTitle:newEntryTitle text:#"-"
created:[NSDate date]];
[entriesArray addObject:anEntry];
[self.tableView reloadData];
[anEntry release];
[self writeDataToArchive];
}
- (void)viewDidLoad
{
[super viewDidLoad];
NSString *filePath = [self dataFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
NSData *data = [[NSMutableData alloc]
initWithContentsOfFile:[self dataFilePath]];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]
initForReadingWithData:data];
NSMutableArray *array = [unarchiver decodeObjectForKey:#"entriesArray"];
entriesArray = [array mutableCopy];
[array release];
[unarchiver finishDecoding];
[unarchiver release];
[data release];
}
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:
(NSIndexPath *)indexPath
{
// ... some other stuff
NSUInteger row = indexPath.row;
Entry *entry = [entriesArray objectAtIndex:row];
cell.textLabel.text = entry.title;
return cell;
}
Thanks a lot.

Answer 1

When you read an array back out with NSKeyedUnarchivers you always get an unmutable copy back. You would need to declare *array as NSArray or just get rid of array all together.
entriesArray = [[unarchiver decodeObjectForKey:#"entriesArray"] mutableCopy];
And #JeremyP points out another issue. Since you didn't alloc or retain *array you should not release it.

Answer 2

You should not release array in viewDidLoad because you do not own it.
Please review the Cocoa memory management Rules because there are a couple of other memory management issues in your code. In particular,
self.title = [[aDecoder decodeObjectForKey:#"title"] retain];
self.text = [[aDecoder decodeObjectForKey:#"text"] retain];
self.created = [[aDecoder decodeObjectForKey:#"created"] retain];
in your initWithCoder: method all leak on the assumption the properties are retain or copy.