How to update coredata value in Objective-C - ios

Question

I am new in iOS and I am facing a problem regarding to update value of coredata.
For Save
NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObject *device;
if (self.device) {
// Update existing device
[device setValue:GlobalIndexPath forKey:#"key"];
} else {
// Create a new device
NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:#"Device" inManagedObjectContext:context];
[newDevice setValue:GlobalIndexPath forKey:#"key"];
}
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
My code to fetch core data is
NSManagedObjectContext *context = [self managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:#"EntityName" inManagedObjectContext:context]];
NSError *error = nil;
NSArray *results = [context executeFetchRequest:request error:&error];
And to update I and using code
NSManagedObject* favoritsGrabbed = [results objectAtIndex:0];
[favoritsGrabbed setValue:#"1" forKey:#"Key"];
Update code not update it add one object.
Note - GlobalIndexPath is a name of string.
But this is not working for me any suggestion. Thanks in Advcance!

Answer 1

You need to save the context every time you make changes to any NSManagedObject and want it to persist. Try this:
NSManagedObject* favoritsGrabbed = [results objectAtIndex:0];
[favoritsGrabbed setValue:#"1" forKey:#"Key"];
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}