Core Data Managed Object Context Saving Problem

Question

I am trying to save an array into core data using NSData but my ManagedObjectContext says there are 0 objects and when I call it, I have it appearing as NULL. I have an entity called Event and 3 attributes in it (chatArray,...,...). I have tried for 11 hours and can't figure it out. I believe I am setting it wrong because the NSData is correct. How should I be setting this???

UPDATE

I am developing a chat application and I have the chat messages in a table view (It's an array of data). I need to save all the chat history when you exit the app and reload it. I have the messages coming in as strings and add it to the array for the table. If I didn't do an array, and I added the messages as strings of text to core data how would I add them to the array for the table view when you reload the app?

@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain) NSManagedObject *managedObject;

//

NSArray *array = [[[NSArray alloc]initWithObjects:@"one",@"two",@"three", nil]autorelease];
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];
NSLog(@"data %@",data);

NSLog(@"Array %@",[NSKeyedUnarchiver unarchiveObjectWithData:data]);

[(Event*)managedObject setValue:data forKey:@"chatArray"];

if ([self managedObject])
{
    NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
    [fetchRequest setEntity:[NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext]];
    [(Event *)managedObject setChatArray:data];              }
else {
    Event *event = [[[Event alloc] initInsertingIntoManagedObjectContext:managedObjectContext]autorelease];
    NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
    [fetchRequest setEntity:[NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext]];
    [event setChatArray:data];
}

NSError *error;
[managedObjectContext save:&error];

NSArray *myArray = [NSKeyedUnarchiver unarchiveObjectWithData:[(Event*)managedObject valueForKey:@"chatArray"]];

NSLog(@"chatArray %@",myArray);

Answer 1

Brandon,

First, in Core Data, BLOBs should be stored in leaf nodes (ie an entity that just contains the BLOB and a back to one relationship. (This pattern/convention has emerged because it is almost trivial to get a retain cycle of large blobs when there are other relations in the entity.)

Second, why are you storing these strings as an array and not as an entity with a time stamp, etc.?A BLOB is not particularly more efficient than individual rows plus the system can both search the messages and more flexibly store the rows. SQLite handles strings specially.

Third, it appears that you are composing your class rather than inheriting from your model entity, why? This makes your code more complex.

Finally, It is really hard to tell what you are trying to do. Could you include your full .h file? And the full method declaration?

Andrew