// Objective-C
[[self saveAsync:obj] continueWithBlock:^id(BFTask *task) {
  if (task.isCancelled) {
    // the save was cancelled.
  } else if (task.error) {
    // the save failed.
  } else {
    // the object was saved successfully.
    PFObject *object = task.result;
  }
  return nil;
}];

// Objective-C
/**
 * Gets an NSString asynchronously.
 */
- (BFTask *)getStringAsync {
  // Let's suppose getNumberAsync returns a BFTask whose result is an NSNumber.
  return [[self getNumberAsync] continueWithBlock:^id(BFTask *task) {
    // This continuation block takes the NSNumber BFTask as input,
    // and provides an NSString as output.

    NSNumber *number = task.result;
    return [NSString stringWithFormat:@"%@", number];
  )];
}

// Objective-C
[[self saveAsync:obj] continueWithSuccessBlock:^id(BFTask *task) {
  // the object was saved successfully.
  return nil;
}];

// Objective-C
PFQuery *query = [PFQuery queryWithClassName:@"Student"];
[query orderByDescending:@"gpa"];
[[[[[self findAsync:query] continueWithSuccessBlock:^id(BFTask *task) {
  NSArray *students = task.result;
  PFObject *valedictorian = [students objectAtIndex:0];
  [valedictorian setObject:@YES forKey:@"valedictorian"];
  return [self saveAsync:valedictorian];
}] continueWithSuccessBlock:^id(BFTask *task) {
  PFObject *valedictorian = task.result;
  return [self findAsync:query];
}] continueWithSuccessBlock:^id(BFTask *task) {
  NSArray *students = task.result;
  PFObject *salutatorian = [students objectAtIndex:1];
  [salutatorian setObject:@YES forKey:@"salutatorian"];
  return [self saveAsync:salutatorian];
}] continueWithSuccessBlock:^id(BFTask *task) {
  // Everything is done!
  return nil;
}];

// Objective-C
PFQuery *query = [PFQuery queryWithClassName:@"Student"];
[query orderByDescending:@"gpa"];
[[[[[self findAsync:query] continueWithSuccessBlock:^id(BFTask *task) {
  NSArray *students = task.result;
  PFObject *valedictorian = [students objectAtIndex:0];
  [valedictorian setObject:@YES forKey:@"valedictorian"];
  // Force this callback to fail.
  return [BFTask taskWithError:[NSError errorWithDomain:@"example.com"
                                                   code:-1
                                               userInfo:nil]];
}] continueWithSuccessBlock:^id(BFTask *task) {
  // Now this continuation will be skipped.
  PFQuery *valedictorian = task.result;
  return [self findAsync:query];
}] continueWithBlock:^id(BFTask *task) {
  if (task.error) {
    // This error handler WILL be called.
    // The error will be the NSError returned above.
    // Let's handle the error by returning a new value.
    // The task will be completed with nil as its value.
    return nil;
  }
  // This will also be skipped.
  NSArray *students = task.result;
  PFObject *salutatorian = [students objectAtIndex:1];
  [salutatorian setObject:@YES forKey:@"salutatorian"];
  return [self saveAsync:salutatorian];
}] continueWithSuccessBlock:^id(BFTask *task) {
  // Everything is done! This gets called.
  // The task's result is nil.
  return nil;
}];

// Objective-C
- (BFTask *)successAsync {
  BFTaskCompletionSource *successful = [BFTaskCompletionSource taskCompletionSource];
  [successful setResult:@"The good result."];
  return successful.task;
}

- (BFTask *)failAsync {
  BFTaskCompletionSource *failed = [BFTaskCompletionSource taskCompletionSource];
  [failed setError:[NSError errorWithDomain:@"example.com" code:-1 userInfo:nil]];
  return failed.task;
}

// Objective-C
BFTask *successful = [BFTask taskWithResult:@"The good result."];

BFTask *failed = [BFTask taskWithError:anError];

// Objective-C
- (BFTask *) fetchAsync:(PFObject *)object {
  BFTaskCompletionSource *task = [BFTaskCompletionSource taskCompletionSource];
  [object fetchInBackgroundWithBlock:^(PFObject *object, NSError *error) {
    if (!error) {
      [task setResult:object];
    } else {
      [task setError:error];
    }
  }];
  return task.task;
}

// Objective-C
PFQuery *query = [PFQuery queryWithClassName:@"Comments"];
[query whereKey:@"post" equalTo:@123];

[[[self findAsync:query] continueWithBlock:^id(BFTask *task) {
  NSArray *results = task.result;

  // Create a trivial completed task as a base case.
  BFTask *task = [BFTask taskWithResult:nil];
  for (PFObject *result in results) {
    // For each item, extend the task with a function to delete the item.
    task = [task continueWithBlock:^id(BFTask *task) {
      // Return a task that will be marked as completed when the delete is finished.
      return [self deleteAsync:result];
    }];
  }
  return task;
}] continueWithBlock:^id(BFTask *task) {
  // Every comment was deleted.
  return nil;
}];

// Objective-C
PFQuery *query = [PFQuery queryWithClassName:@"Comments"];
[query whereKey:@"post" equalTo:@123];

[[[self findAsync:query] continueWithBlock:^id(BFTask *results) {
  // Collect one task for each delete into an array.
  NSMutableArray *tasks = [NSMutableArray array];
  for (PFObject *result in results) {
    // Start this delete immediately and add its task to the list.
    [tasks addObject:[self deleteAsync:result]];
  }
  // Return a new task that will be marked as completed when all of the deletes are
  // finished.
  return [BFTask taskForCompletionOfAllTasks:tasks];
}] continueWithBlock:^id(BFTask *task) {
  // Every comment was deleted.
  return nil;
}];

// Create a BFExecutor that uses the main thread.
BFExecutor *myExecutor = [BFExecutor executorWithBlock:^void(void(^block)()) {
  dispatch_async(dispatch_get_main_queue(), block);
}];

// And use the Main Thread Executor like this. The executor applies only to the new
// continuation being passed into continueWithBlock.
[[self fetchAsync:object] continueWithExecutor:myExecutor withBlock:^id(BFTask *task) {
    myTextView.text = [object objectForKey:@"name"];
}];

// Continue on the Main Thread, using a built-in executor.
[[self fetchAsync:object] continueWithExecutor:[BFExecutor mainThreadExecutor] withBlock:^id(BFTask *task) {
    myTextView.text = [object objectForKey:@"name"];
}];

- (void)doSomethingComplicatedAsync:(MYCancellationToken *)cancellationToken {
    [[self doSomethingAsync:cancellationToken] continueWithBlock:^{
        if (cancellationToken.isCancelled) {
            return [BFTask cancelledTask];
        }
        // Do something that takes a while.
        return result;
    }];
}

// Somewhere else.
MYCancellationToken *cancellationToken = [[MYCancellationToken alloc] init];
[obj doSomethingComplicatedAsync:cancellationToken];

// When you get bored...
[cancellationToken cancel];

- (BOOL)application:(UIApplication *)application
            openURL:(NSURL *)url
  sourceApplication:(NSString *)sourceApplication
         annotation:(id)annotation {
    BFURL *parsedUrl = [BFURL URLWithInboundURL:url sourceApplication:sourceApplication];

    // Use the target URL from the App Link to locate content.
    if ([parsedUrl.targetURL.pathComponents[1] isEqualToString:@"profiles"]) {
        // Open a profile viewer.
    }

    // You can also check the query string easily.
    NSString *query = parsedUrl.targetQueryParameters[@"query"];

    // Apps that have existing deep-linking support and map their App Links to existing
    // deep-linking functionality may instead want to perform these operations on the input URL.
    // Use the target URL from the App Link to locate content.
    if ([parsedUrl.inputURL.pathComponents[1] isEqualToString:@"profiles"]) {
        // Open a profile viewer.
    }

    // You can also check the query string easily.
    NSString *query = parsedUrl.inputQueryParameters[@"query"];

    // Apps can easily check the Extras and App Link data from the App Link as well.
    NSString *fbAccessToken = parsedUrl.appLinkExtras[@"fb_access_token"];
    NSDictionary *refererData = parsedUrl.appLinkExtras[@"referer"];
}

[BFAppLinkNavigation navigateToURLInBackground:url];

[[BFAppLinkNavigation resolveAppLinkInBackground:url] continueWithSuccessBlock:^id(BFTask *task) {
    BFAppLink *link = task.result;
}];

BFAppLinkNavigation *navigation = [BFAppLinkNavigation navigationWithAppLink:link
                                                                      extras:@{ @"access_token": @"t0kEn" }
                                                                 appLinkData:@{ @"ref": @"12345" }];
NSError *error = nil;
[navigation navigate:&error];

[BFAppLinkNavigation navigateToURLInBackground:url
                                      resolver:resolver];

[BFAppLinkNavigation setDefaultResolver:resolver];
[BFAppLinkNavigation navigateToURLInBackground:url];

- (void)viewDidLoad {
  [super viewDidLoad];

  // Perform other view initialization.

  self.returnToRefererController = [[BFAppLinkReturnToRefererController alloc] init];

  // self.returnToRefererView is a BFAppLinkReturnToRefererView.
  // You may initialize the view either by loading it from a NIB or programmatically.
  self.returnToRefererController.view = self.returnToRefererView;

  // If you have a UINavigationController in the view, then the bar must be shown above it.
  [self.returnToRefererController]
}

- (void)viewWillAppear {
  [super viewWillAppear];

  // Show only if you have a back AppLink.
  [self.returnToRefererController showViewForRefererURL:self.openedAppLinkURL];
}

[[NSNotificationCenter defaultCenter] addObserverForName:BFMeasurementEventNotificationName object:nil queue:nil usingBlock:^(NSNotification *note) {
    NSDictionary *event = note.userInfo;
    NSDictionary *eventData = event[BFMeasurementEventArgsKey];
    // Integrate to your logging/analytics component.
}];