Core Data app crashes on saving - objective-c

Question

I got the following error [context save:&error]. How should I fix?
unrecognized selector sent to class
* -[NSKeyedArchiver dealloc]: warning: NSKeyedArchiver deallocated without having had -finishEncoding called on it.
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[TempObject encodeWithCoder:]:
unrecognized selector sent to class'
Here the code I'm using.
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
PostRequest *postRequestObject = (PostRequest *)[NSEntityDescription insertNewObjectForEntityForName:#"PostRequest" inManagedObjectContext:context];
DummyClass *request = OtherClassObject;
postRequestObject.request = request;
// request is attribute with type transformable
NSLog(#"requestpost data -> %#",postRequestObject.request);
NSError *error = nil;
if (![context save:&error]) {
// Replace this implementation with code to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
#pragma mark - private method
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil)
{
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"PostRequest" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:80];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"status" ascending:NO];
NSArray *sortDescriptors = #[sortDescriptor];
[sortDescriptor autorelease];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"root"] autorelease];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}

Answer 1

The error message says that you have a class named TempObject, that you're trying to call encodeWithCoder: on it, and that this class does not implement that method. That's a crashing bug, as you're seeing.
It seems that you have a transformable Core Data attribute somewhere, and that you're assigning an instance of TempObject to this attribute. I don't know where that is. Your code snippet mentions a transformable attribute, but you don't use TempObject in the code. I can't tell if this code is not actually the cause of the crash or if you changed the name by hand for some reason.
Anyway, when you have a transformable attribute, you must do one of two things:
Make your class conform to NSCoding. You said in a comment that you did, but your error message says that you didn't-- or at least, that you didn't finish the job. NSCoding defines two methods, initWithCoder: and encodeWithCoder:, and your class must implement both of them.
Create a custom NSValueTransformer subclass that can convert your object to/from NSData, and configure your Core Data model to use this. Apple provides a couple of really good (but simple) examples of how to do this.
Anything you assign to a transformable attribute must do one of these. Which one is up to you.
It seems that you're trying to do #1 but haven't finished the job. Make sure that your class conforms to NSCoding.