Login with Facebook in iOS programmatically

Integrating facebook in any iOS application for login purpose is common in today's market. As most of today's applications uses login through facebook and almost every general user has an facebook account, most applications relies on this media for getting user details. Facbook provides its own SDK that you can use for your app. There are separate SDK for both iOS and android. You can also find Sample code that you can use with your code. I have recently used facebook integration in my iOS application. I am sharing my code with you for integrating Facebook in iOS programmatically. Hope it would be helpful:
Adding a Facebook Login Button

UIButton *facebook = [UIButton buttonWithType:UIButtonTypeRoundedRect];
facebook.frame = CGRectMake(0, 0, 150,50);
facebook.center = self.center;
[facebook setTitleEdgeInsets:UIEdgeInsetsMake(0.0f, 30.0f, 0.0f, 0.0f)];
[facebook setTitle:@" Sign in with Facebook " forState:(UIControlStateNormal&UIControlStateHighlighted&UIControlStateSelected)];
[facebook setTitleColor:[UIColor whiteColor] forState:UIControlStateHighlighted];
[facebook setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
[facebook setTitleColor:[UIColor whiteColor] forState:UIControlStateSelected];
[facebook.titleLabel setFont:[UIFont fontWithName:@"Arial" size:14]];
[facebook addTarget:self action:@selector(facebooklogin:) forControlEvents:UIControlEventTouchDown];
[self.view addSubview:facebook];
-(void)facebooklogin:(id)sender { 
    [[NSUserDefaults standardUserDefaults]setInteger:1 forKey:@"FBonBackGround"];
    [self ShowActivityIndicatorWithTitle:@"Loading..."];
    Reachability *reach = [Reachability reachabilityForInternetConnection];
    NetworkStatus netStatus = [reach currentReachabilityStatus];
   
    if (netStatus == NotReachable) {
        [self HideActivityIndicator];
        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Connection Failed" message:@"No internet connection available" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [alert show];
    } else {
        if (FBSession.activeSession.isOpen ) {
            [self UserInformation];
        } else {
            NSArray *permissions = [[NSArray alloc] initWithObjects:@"email",@"user_photos",@"user_birthday",@"read_friendlists", nil];
           // NSArray *permissions = [[NSArray alloc] initWithObjects:@"read_friendlists",@"user_photos",nil];
            [FBSession openActiveSessionWithReadPermissions:permissions allowLoginUI:YES completionHandler:^(FBSession *session, FBSessionState status, NSError *error)
//             [FBSession openActiveSessionWithPublishPermissions:permissions defaultAudience:FBSessionDefaultAudienceEveryone allowLoginUI:YES completionHandler:^(FBSession *session, FBSessionState status, NSError *error) {
                 if(!error) {
                     [self UserInformation];
                 } else {
                     NSLog(@"Error : %@",error);
                     UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Facebook Error" message:@"Picture Guesser uses your Facebook identity to make sure you're real. You'll need to accept to join!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                     [alert show];
                     [self HideActivityIndicator];
                 }
             }];
        }
    }
}
-(void)UserInformation { 
    Reachability *reach = [Reachability reachabilityForInternetConnection];
    NetworkStatus netStatus = [reach currentReachabilityStatus];
    if (netStatus == NotReachable) {
        [self HideActivityIndicator];
        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Connection Failed" message:@"No internet connection available" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [alert show];
    } else {
        [[FBRequest requestForGraphPath:@"me"] startWithCompletionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
            if(!error ) {
                [self ShowActivityIndicatorWithTitle:@"Loading..."];
                [[[FBSession activeSession] accessTokenData] accessToken];
                NSLog(@"acces token=%@",[[[FBSession activeSession] accessTokenData] accessToken]);
                [[NSUserDefaults standardUserDefaults]setValue:[[[FBSession activeSession] accessTokenData] accessToken]  forKey:@"FbAccessTokenKey"];
                NSLog(@"sdfsdfdsfsf=%@",[[NSUserDefaults standardUserDefaults] valueForKey:@"FbAccessTokenKey"]);
                NSLog(@"result %@",result);
                NSString *userName=[result objectForKey:@"name"];
                NSString *userid=[result objectForKey:@"id"];
                NSString *email = [result objectForKey:@"email"];
                NSString *gender = [result objectForKey:@"gender"];
                NSString *dob = [result objectForKey:@"birthday"];
                NSString *userLocation  = [[result objectForKey:@"location"] objectForKey:@"name"];         
            }
        }];
    }
}
- (void)ShowActivityIndicatorWithTitle:(NSString *)Title { 
    [SVProgressHUD showWithStatus:Title maskType:SVProgressHUDMaskTypeGradient];
    [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.01]];
}
- (void)HideActivityIndicator { 
    [SVProgressHUD dismiss];
} 

In the above code I have used the SVDProgressHUD for displaying the loading indicator. The Reachability class is used for checking the net connection. One thing to take into consideration is that before adding Facebook in iOS programmatically you should first go to facebook developer account and create a facebook app for your respective iOS application. After creating the facebook app for your iOS application you will get an Facebook ID for your app that you will be using in your app to connect with facebook.