Signing new user up in parse

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}


/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

- (IBAction)login:(id)sender {
    NSString *username = [self.usernameField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSString *password = [self.passwordField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];;

    if([username length] == 0 ||[password length] ==0) {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Oops!" message:@"Make sure you enter a username and password!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

        [alertView show];
    }
    else {
        [PFUser logInWithUsernameInBackground:username password:password
                                        block:^(PFUser *user, NSError *error) {
                                            if (error) {
                                                UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Sorry!" message:[error.userInfo objectForKey:@"error"] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                                                [alertView show];
                                            }
                                            else {
                                                [self.navigationController popToRootViewControllerAnimated:YES];
                                            }
                                        }];
        }