Simple NSManagedObject update observer

ADVManagedObjectController.h

//
//  Copyright © 2013 Yuri Kotov
//

#import <Foundation/Foundation.h>

typedef void(^ADVManagedObjectHandler)(id object);

@interface ADVManagedObjectController : NSObject

@property (readonly, nonatomic) NSManagedObject *object;
@property (strong, nonatomic) ADVManagedObjectHandler handler;

- (instancetype) initWithObject:(NSManagedObject *)object;

@end

ADVManagedObjectController.m

//
//  Copyright © 2013 Yuri Kotov
//

#import "ADVManagedObjectController.h"

@interface ADVManagedObjectController ()
@property (strong, nonatomic) NSManagedObject *object;
@end

@implementation ADVManagedObjectController

- (instancetype) initWithObject:(NSManagedObject *)object
{
    if ((self = [super init]))
    {
        _object = object;
        [self startNotifying];
    }
    return self;
}

- (void) startNotifying
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(contextDidChange:)
                                                 name:NSManagedObjectContextObjectsDidChangeNotification
                                               object:self.object.managedObjectContext];
}

- (void) stopNotifying
{
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:NSManagedObjectContextObjectsDidChangeNotification
                                                  object:self.object.managedObjectContext];
}

- (void) contextDidChange:(NSNotification *)notification
{
    if (self.handler)
    {
        NSSet *update = notification.userInfo[NSUpdatedObjectsKey];
        if ([update containsObject:self.object]) self.handler(self.object);
    }
}

- (void) dealloc
{
    [self stopNotifying];
}

@end