[VTFollowOnTwitter followUsername:@"test"
            fromPreferredUsername:nil
                          success:^{ /* Good */ }
                 multipleAccounts:^(NSArray *usernames) { /* Need specific username */ } 
                          failure:^(NSError *error) { /* Not good */ }];

@interface VTViewController : UIViewController

- (IBAction)followOnTwitter:(id)sender;

@end

// ---
@interface VTViewController () <UIActionSheetDelegate>

- (void)followOnTwitterFromUsername:(NSString *)fromUsername;

@end


@implementation VTViewController

- (IBAction)followOnTwitter:(id)sender {
    [self followOnTwitterFromUsername:nil];
}

- (void)followOnTwitterFromUsername:(NSString *)fromUsername {
    NSString *username = @"StudioAMANgA";

    [VTFollowOnTwitter followUsername:username fromPreferredUsername:fromUsername success:^{
        [[[UIAlertView alloc] initWithTitle:@"Thanks!" message:nil delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] show];
    } multipleAccounts:^(NSArray *usernames) {
        UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Which account do you want to follow us with?" delegate:self cancelButtonTitle:nil destructiveButtonTitle:nil otherButtonTitles:nil];
        for (NSString *username in usernames)
            [actionSheet addButtonWithTitle:[@"@" stringByAppendingString:username]];
        [actionSheet addButtonWithTitle:@"Cancel"];
        [actionSheet setCancelButtonIndex:[usernames count]];
        [actionSheet showInView:self.view];
    } failure:^(NSError *error) {
        [[[UIAlertView alloc] initWithTitle:@"Request Error" message:[NSString stringWithFormat:@"Sorry, something went wrong.\n%@", [error localizedDescription]] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] show];
    }];
}

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (buttonIndex != actionSheet.cancelButtonIndex) {
        [self followOnTwitterFromUsername:[[actionSheet buttonTitleAtIndex:buttonIndex] stringByReplacingOccurrencesOfString:@"@" withString:@""]];
    }
}

@end