iOS app users in a ui list

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

@interface ViewController : UIViewController<FBLoginViewDelegate>

@property (weak,nonatomic) IBOutlet UIButton *registerBtn;
@property (weak,nonatomic) IBOutlet UIButton *loginBtn;
@property (weak,nonatomic) IBOutlet UITextField *usernameField;
@property (weak,nonatomic) IBOutlet UITextField *passwordField;
@property (weak,nonatomic) IBOutlet UITextField *reEnterPasswordField;

@property (weak,nonatomic) IBOutlet FBLoginView *loginView;

- (IBAction)registerUser:(id)sender;
- (IBAction)LoginUser:(id)sender;


@end

#import "ViewController.h"
#import "loggedViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    self.loginView.readPermissions = @[@"public_profile", @"email", @"user_friends"];

    
    UIBarButtonItem *NewBackButton =[[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStyleBordered target:nil action:nil];
    [[self navigationItem] setBackBarButtonItem:NewBackButton];
    
    [super viewDidLoad];
	NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if (![defaults boolForKey:@"registered"]) {
        NSLog(@"no user registered");
        _loginBtn.hidden = YES;
    }
    else {
        NSLog(@"user is registered");
        _reEnterPasswordField.hidden = YES;
        _registerBtn.hidden = YES;
    }
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)registerUser:(id)sender {
    if ([_usernameField.text isEqualToString:@""] || [_passwordField.text isEqualToString:@""] ||
        [_reEnterPasswordField.text isEqualToString:@""]){
        UIAlertView *error = [[UIAlertView alloc] initWithTitle:@"Ooops" message:@" You must complete all fields" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [error show];
    }
    else{
        [self checkPasswordsMatch];
    }
}

-(void) checkPasswordsMatch {
    if ([_passwordField.text isEqualToString:_reEnterPasswordField.text]) {
        NSLog(@"passwords match!");
        [self registerNewUser];
    }
    else{
        NSLog(@"passwords don't match");
        UIAlertView *error = [[UIAlertView alloc] initWithTitle:@"Ooops" message:@" passwords don't match" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [error show];
    }

}
- (void) registerNewUser {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    
    [defaults setObject:_usernameField.text forKey:@"username"];
    [defaults setObject:_passwordField.text forKey:@"password"];
    [defaults setBool:YES forKey:@"registered"];
    
    [defaults synchronize];
    
    UIAlertView *success = [[UIAlertView alloc] initWithTitle:@"Success" message:@" Your profile has been created!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [success show];
    
    [self performSegueWithIdentifier:@"login" sender:self];

}

-(IBAction)LoginUser:(id)sender {
    
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    
    if ([_usernameField.text isEqualToString:[defaults objectForKey:@"username"]] && [_passwordField.text isEqualToString:[defaults objectForKey:@"password"]]) {
        //_usernameField.text = nil;
        _passwordField.text = nil;
        [self performSegueWithIdentifier:@"login" sender:self];
        
    }
    else {
        NSLog(@"passwords don't match");
        UIAlertView *error = [[UIAlertView alloc] initWithTitle:@"Ooops" message:@"Your username or password does not match" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [error show];

    }
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.destinationViewController isKindOfClass:[loggedViewController class]])
    {
        loggedViewController *viewController = segue.destinationViewController;
        viewController.userName = self.usernameField.text;
        
    }
}


- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user
{
    NSLog(@"%@", user.name);
}

- (void)loginViewShowingLoggedInUser:(FBLoginView *)loginView
{
    NSLog(@"You are logged in! :) ");
    
}

- (void)loginViewShowingLoggedOutUser:(FBLoginView *)loginView
{
    NSLog(@"You are logged out! :( ");
}

- (void)loginView:(FBLoginView *)loginView handleError:(NSError *)error
{
    NSString *alertMessage, *alertTitle;
    
    if ([FBErrorUtility shouldNotifyUserForError:error])
    {
        alertTitle = @"Facebook error";
        alertMessage = [FBErrorUtility userMessageForError:error];
        
    }
    else if ([FBErrorUtility errorCategoryForError:error] == FBErrorCategoryAuthenticationReopenSession)
    {
        alertTitle = @"Session Error";
        alertMessage = @"Your current session is no longer valid. Please log in again.";
        
    }
    else if ([FBErrorUtility errorCategoryForError:error] == FBErrorCategoryUserCancelled)
    {
        NSLog(@"user cancelled login");
        
    }
    else
    {
        alertTitle  = @"Something went wrong";
        alertMessage = @"Please try again later.";
        NSLog(@"Unexpected error:%@", error);
    }
    
    if (alertMessage)
    {
        [[[UIAlertView alloc] initWithTitle:alertTitle
                                    message:alertMessage
                                   delegate:nil
                          cancelButtonTitle:@"OK"
                          otherButtonTitles:nil] show];
    }
}

@end

#import "AppDelegate.h"
#import <FacebookSDK/FacebookSDK.h>


@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [FBLoginView class];
    return YES;
}
							
- (void)applicationWillResignActive:(UIApplication *)application
{
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

@end