CoreData in ios

#import "AppDelegate.h"

Allocation -
- (NSManagedObjectContext *)managedObjectContext {
    NSManagedObjectContext *context = nil;
    id delegate = [[UIApplication sharedApplication] delegate];
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }
    return context;
}


Adding Data -
 NSManagedObjectContext *context = [self managedObjectContext];
   
    // Create a new managed object
    NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"Device" inManagedObjectContext:context];
    [newDevice setValue:@"1" forKey:@"id"];
    [newDevice setValue:@"Rince" forKey:@"name"];
   
   
    NSError *error = nil;
    // Save the object to persistent store
    if (![context save:&error]) {
        NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
    }

Display Data -
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Device"];
    self.devices = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];
NSManagedObject *device = [self.devices objectAtIndex:indexPath.row];
    [cell.textLabel setText:[NSString stringWithFormat:@"%@ %@",[device valueForKey:@"id"], [device valueForKey:@"name"]]];