NSFetchedResultsController - only show results saved in database? - ios

Question

I'm using Core Data and an NSManagedObject as the object model for temporarily storing the data in the app before it's saved.
Then in a tableview I display all saved instances. However, the temporary object is also appearing in the list. How can I ensure my tableview only displays results that are actually saved in the database?
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"State" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"timeStamp" ascending:NO];
NSArray *sortDescriptors = #[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Master"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}

Answer 1

You can set
[fetchRequest setIncludesPendingChanges:NO];
From the documentation:
The default value is YES.
If the value is NO, the fetch request skips checking unsaved changes
and only returns objects that matched the predicate in the persistent
store.

Answer 2

NSManagedObjectContext NSFetchedResultsController will automatically save the context. So your change is already saved to database before you restore data in tableView
Core Data can manage data in-memory, which is describe as :
Core Data provides an infrastructure for change management and for
saving objects to and retrieving them from storage. It can use SQLite
as one of its persistent store types. It is not, though, in and of
itself a database. (To emphasize this point: you could for example use
just an in-memory store in your application. You could use Core Data
for change tracking and management, but never actually save any data
in a file.)
to solve your problem, you can create another NSManagedObjectContext, which use to save your temporary data. when you want to save these temp data to your database, just create new NSManagedObject and copy the data info from de temp data and save it to your permanent database context