two_requests.m

#import <Bolts/Bolts.h>

@property (strong, nonatomic) BFTask *backgroundRequest1;

- (BFTask<NSData *> *)dataTaskWithURL:(NSURL *)url
{
    BFTaskCompletionSource *taskCompletionSource = [BFTaskCompletionSource taskCompletionSource];
    NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url
                                                             completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
                                                                 NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) response;
                                                                 if (httpResponse.statusCode == 200 && !error && data) {
                                                                     [taskCompletionSource setResult:data];
                                                                 } else {
                                                                     [taskCompletionSource setError:error];
                                                                 }
                                                             }];

    [task resume];
    return taskCompletionSource.task;
}

- (BFTask *)request1
{
    return [self dataTaskWithURL:"URL1"];
}

- (BFTask *)request2
{
    return [self dataTaskWithURL:"URL2"];
}

- (void)viewDidLoad
{
    backgroundRequest1 = [self request1];
}

- (void)handleClick
{
    __weak weakSelf = self;
    [[[backgroundRequest1 continueWithBlock:^id(BFTask *task) {
        if (task.error) {
            return [weakSelf request1];
        }
        return [BFTask taskWithResult:task.result];
    }] continueWithSuccessBlock:^id(BFTask *task) {
        return [weakSelf request2];
    }] continueWithBlock:^id(BFTask *task) {
        if (task.error) {
            // show alert!
        } else {
            // show next screen
        }
        return nil;
    }];
}