Log in to Google OAuth 2.0 on iOS

Question

I am writing an application that should display the current AdSense data, my problem is that every time I open the application, they prompt me with GTMAuth2ViewControllerTouch, so the familiar Google OAuth 2.0 login screen (I used this to make the login material). How can I log in once and then the user will be signed forever? There is kKeychainItemName in the tutorial, but this is just a string, how can I use this to automatically log in a user? Take a look at ViewDidLoad.

This is the code I'm using:

#import "ViewController.h" #import "GTMOAuth2Authentication.h" #import "GTMOAuth2ViewControllerTouch.h" #import "GTMOAuth2SignIn.h" #import "GTMHTTPFetcher.h" static NSString *const kKeychainItemName = @"OAuth2 AdZen: AdSense"; NSString *kMyClientID = @"xxxxxxxxx.apps.xxxxxxxxxxxxx.com"; // pre-assigned by service NSString *kMyClientSecret = @"xxxxxxxxxx--xxxxx"; // pre-assigned by service NSString *scope = @"https://www.googleapis.com/auth/adsense.readonly"; // scope for Google+ API @interface ViewController () @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; if (/*USER ALREADY LOGGED IN*/) { //DO THE LOGIN STUFF AUTOMATICALLY WITH THE KEYCHAINITEM } else { [self signInToGoogle]; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } -(void)signInToGoogle { GTMOAuth2ViewControllerTouch *viewController; viewController = [[GTMOAuth2ViewControllerTouch alloc] initWithScope:scope clientID:kMyClientID clientSecret:kMyClientSecret keychainItemName:kKeychainItemName delegate:self finishedSelector:@selector(viewController:finishedWithAuth:error:)]; [self.navigationController pushViewController:viewController animated:YES]; } - (void)viewController:(GTMOAuth2ViewControllerTouch *)viewController finishedWithAuth:(GTMOAuth2Authentication *)auth error:(NSError *)error { if (error != nil) { // Authentication failed UIAlertView *fail = [[UIAlertView alloc] initWithTitle:@"AdZen" message:[NSString stringWithFormat:@"Error, Authentication failed!\n %@",error] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:@"Try again", nil]; fail.tag = 1; [fail show]; NSLog(@"Authentication failed!"); } else { // Authentication succeeded UIAlertView *success = [[UIAlertView alloc] initWithTitle:@"AdZen" message:[NSString stringWithFormat:@"Authentication succeeded!"] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; success.tag = 2; [success show]; NSLog(@"Autzentication succeeded!"); } } -(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (buttonIndex == 1) { if (alertView.tag == 1) { [self signInToGoogle]; } } } - (void)authentication:(GTMOAuth2Authentication *)auth request:(NSMutableURLRequest *)request finishedWithError:(NSError *)error { if (error != nil) { NSLog(@"Authentication failed! 1"); } else { // Authentication succeeded NSLog(@"Autzentication succeeded! 1"); } } - (void)awakeFromNib { // Get the saved authentication, if any, from the keychain. GTMOAuth2Authentication *auth; auth = [GTMOAuth2ViewControllerTouch authForGoogleFromKeychainForName:kKeychainItemName clientID:kMyClientID clientSecret:kMyClientSecret]; // Retain the authentication object, which holds the auth tokens // // We can determine later if the auth object contains an access token // by calling its -canAuthorize method //[self setAuthentication:auth]; //NSLog(@"Already logged in!"); } -(IBAction)signout { [GTMOAuth2ViewControllerTouch removeAuthFromKeychainForName:kKeychainItemName]; UIAlertView *signedout = [[UIAlertView alloc] initWithTitle:@"AdZen" message:@"You just signed out, please sign in to see your AdSense info." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [signedout show]; [self signInToGoogle]; } 

Answer 1

In the "awakeFromNib:" method, check if the authentication is verified, if the user has already been signed in. If the user is already signed up, go to the next view or the next screen that you want to take from the user after signing up.

 -(void)awakeFromNib { GTMOAuth2Authentication *auth = nil; auth = [GTMOAuth2ViewControllerTouch authForGoogleFromKeychainForName:kKeychainItemName clientID:kMyClientID clientSecret:kMyClientSecret]; //Retain the authentication object, which holds the auth tokens [self setAuthentication:auth]; //self.auth = auth; if([self isSignedIn]) { NextViewController *nextViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"NextViewController"]; [self.navigationController pushViewController:nextViewController animated:YES]; } } - (void)setAuthentication:(GTMOAuthAuthentication *)auth { mAuth = nil; mAuth = [auth retain]; } 

Here you can check if the user is allowed by calling the -canAuthorize method. It checks for authorization and returns a true flag if enabled.

 (BOOL)isSignedIn { BOOL isSignedIn = self.auth.canAuthorize; return isSignedIn; }