键值的依赖关系

- (NSString *)fullName {

    return [NSString stringWithFormat:@"%@ %@",firstName, lastName];

}

+ (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key

{

    NSSet *keyPaths = [super keyPathsForValuesAffectingValueForKey:key];

    if ([key isEqualToString:@"fullName"])

    {

        NSSet *affectingKeys = [NSSet setWithObjects:@"lastName", @"firstName",nil];

        keyPaths = [keyPaths setByAddingObjectsFromSet:affectingKeys];

    }

    return keyPaths;

}

+ (NSSet *)keyPathsForValuesAffectingFullName

{

    return [NSSet setWithObjects:@"lastName", @"firstName", nil

}