Using Background Fetching with Core Data - objective-c

Question

I am going through the "iOS 7 Programming Cookbook" and I can't seem to run the script based on the title of my question. Basically, I am trying to create some records in the background queue and then get the results in the main queue but nothing gets passed to the console when I run the code. Here are the methods used in the example. What am I missing here?
- (void) populateDatabase{
for (NSUInteger counter = 0; counter < 1000; counter++){
Person *person =
[NSEntityDescription
insertNewObjectForEntityForName:NSStringFromClass([Person class])
inManagedObjectContext:self.managedObjectContext];
person.firstName = [NSString stringWithFormat:#"First name %lu",
(unsigned long)counter];
person.lastName = [NSString stringWithFormat:#"Last name %lu",
(unsigned long)counter];
person.age = #(counter);
}
NSError *error = nil;
if ([self.managedObjectContext save:&error]){
NSLog(#"Managed to populate the database.");
} else {
NSLog(#"Failed to populate the database. Error = %#", error);
}
}
- (void) processPersons:(NSArray *)paramPersons{
for (Person *person in paramPersons){
NSLog(#"First name = %#, last name = %#, age = %ld",
person.firstName,
person.lastName,
(long)person.age.integerValue);
}
}
- (NSFetchRequest *) newFetchRequest{
NSFetchRequest *request = [[NSFetchRequest alloc]
initWithEntityName:
NSStringFromClass([Person class])];
request.fetchBatchSize = 20;
request.predicate =
[NSPredicate predicateWithFormat:#"(age >= 100) AND (age <= 200)"];
request.resultType = NSManagedObjectIDResultType;
return request;
}
- (BOOL) application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
__weak NSManagedObjectContext *mainContext = self.managedObjectContext;
__weak AppDelegate *weakSelf = self;
__block NSMutableArray *mutablePersons = nil;
/* Set up the background context */
NSManagedObjectContext *backgroundContext =
[[NSManagedObjectContext alloc]
initWithConcurrencyType:NSPrivateQueueConcurrencyType];
backgroundContext.persistentStoreCoordinator =
self.persistentStoreCoordinator;
/* Issue a block on the background context */
[backgroundContext performBlock:^{
NSError *error = nil;
NSArray *personIds = [backgroundContext
executeFetchRequest:[weakSelf newFetchRequest]
error:&error];
if (personIds != nil && error == nil){
mutablePersons = [[NSMutableArray alloc]
initWithCapacity:personIds.count];
/* Now go on the main context and get the objects on that
context using their IDs */
dispatch_async(dispatch_get_main_queue(), ^{
for (NSManagedObjectID *personId in personIds){
Person *person = (Person *)[mainContext
objectWithID:personId];
[mutablePersons addObject:person];
}
[weakSelf processPersons:mutablePersons];
});
} else {
NSLog(#"Failed to execute the fetch request.");
}
}];
self.window = [[UIWindow alloc]
initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.backgroundColor = [UIColor whiteColor];
ViewController *viewController = [[ViewController alloc] init];
self.window.rootViewController = viewController;
[self.window makeKeyAndVisible];
return YES;
}