Update issue with Core Data - objective-c

Question

Trying to update some Core Data. The data is actually updating "somewhere", but its not saving/updating the db.
- (IBAction)Update:(id)sender {
NSEntityDescription *entityDesc =
[NSEntityDescription entityForName:#"Preferences"
inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDesc];
NSError *error;
NSArray *objects = [context executeFetchRequest:request
error:&error];
if ([objects count] == 0) {
// No update, didnt find any entries.
} else {
for (NSManagedObject *obj in objects) {
[obj setValue:_salesPrice.text forKey:#"value"];
if(![context save:&error]){
NSLog(#"Saving changes failed: %#", error);
}
}
}
//[context save:&error];
}
I've tried [context save:&error]; in the commented area, but still no save. I also get no error on save.

Answer 1

You use only 1 NSManagedObjectContext? Your naming convention is not ideal. Usually you would name the entity Preference, since its one object. Try the following code.
CoreDataAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
// This is for completion. Usually you should not get the context from the App Delegate.
// Its better to pass it from the App Delegate to
// the initial view controller via a property (dependency injection).
NSFetchRequest *req = [[NSFetchRequest alloc] initWithEntityName:NSStringFromClass([Preferences class])];
NSError *error = nil;
NSArray *preferences = [context executeFetchRequest:req error:&error];
// Check error
if ([preferences count] == 0) {
// No update, didnt find any entries.
} else {
for (Preferences *preference in preferences) {
[preference setValue:_salesPrice.text forKey:#"value"];
}
}
[context save:&error];
// Check error