Release a Login Screen

Question

I have just started getting into coding and have found Parse, which helps you code in a login screen and uses their web databases to store info. I have gotten the login to pop up and is working, but after it accepts my authentication I cannot get it to release the view control screen. Can anybody take a look and see where I'm going wrong?

#import <UIKit/UIKit.h>
#import <Parse/Parse.h>

@interface ViewController : UIViewController <PFLogInViewControllerDelegate>{

}

@end

@implementation ViewController


- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    PFLogInViewController *login = [[PFLogInViewController alloc] init];
    login.fields = PFLogInFieldsUsernameAndPassword | PFLogInFieldsLogInButton;
    login.delegate = self;
    [self presentViewController:login animated:YES completion:nil];
}
- (void)logInViewController:(PFLogInViewController *)logInController didLogInUser:(PFUser *)user {
    [self dismissViewControllerAnimated:YES completion:NULL];
}

- (void)logInViewControllerDidCancelLogIn:(PFLogInViewController *)logInController {
    [self dismissViewControllerAnimated:YES completion:NULL];
}


// Do any additional setup after loading the view, typically from a nib.


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end