Using the Google iOS OAuth2 library for both Twitter and LinkedIn

Google OAuth2 iOS Library with LinkedIn and Twitter.m

- (void)signIn:(int)socialNetworkType {
  //! Method to launch authorization modal dialog for Twitter or LinkedIn

  NSURL *requestURL;
  NSURL *authorizeURL;
  NSURL *accessURL;
  NSString *scope; 
  
  if (socialNetworkType == kSignupSocialLinkedIn) {
    // LinkedIn OAuth token request URLs
    requestURL = [NSURL URLWithString:@"https://api.linkedin.com/uas/oauth/requestToken"];
    authorizeURL = [NSURL URLWithString:@"https://api.linkedin.com/uas/oauth/authorize"];
    accessURL = [NSURL URLWithString:@"https://api.linkedin.com/uas/oauth/accessToken"];
    scope = @"http://api.linkedin.com/";
  }
  if (socialNetworkType == kSignupSocialTwitter) {
    // Twitter OAuth token request URLs
    requestURL = [NSURL URLWithString:@"https://api.twitter.com/oauth/request_token"];
    authorizeURL = [NSURL URLWithString:@"https://api.twitter.com/oauth/authorize"];
    accessURL = [NSURL URLWithString:@"https://api.twitter.com/oauth/access_token"];
    scope = @"http://api.twitter.com/";
  }
  
  // Need to request the authorization object, load your app's API tokens
  GDataOAuthAuthentication *auth = [self authFor:socialNetworkType];
    
    // Try to get authorization from keychain, if user has previously enabled access...    
    BOOL didAuthFromKeychain = NO;
    
    
    if (socialNetworkType == kSignupSocialLinkedIn) {
      didAuthFromKeychain = [GDataOAuthViewControllerTouch authorizeFromKeychainForName:kLinkedInAppServiceName authentication:auth];
    }
    
    if (socialNetworkType == kSignupSocialTwitter) {
      didAuthFromKeychain = [GDataOAuthViewControllerTouch authorizeFromKeychainForName:kTwitterAppServiceName authentication:auth];
    }
    
    if (!didAuthFromKeychain) {
      // Error: could not get authorization from keyChain, so set up a login dialog
      
      
      // Always save value in keyChain
      NSString *keychainAppServiceName;
      
      
      if (socialNetworkType == kSignupSocialLinkedIn) {
        [auth setCallback:@"http://www.linkedin.com/success"];  // set the callback URL 
        keychainAppServiceName = kLinkedInAppServiceName;
      }
      if (socialNetworkType == kSignupSocialTwitter) {
        [auth setCallback:@"http://www.twitter.com/success"]; // set the callback URL 
        keychainAppServiceName = kTwitterAppServiceName;
      }
      
      
      // Display the autentication view.
      GDataOAuthViewControllerTouch *viewController;
      viewController = [[[GDataOAuthViewControllerTouch alloc] initWithScope:scope
                                      language:nil
                                   requestTokenURL:requestURL
                                 authorizeTokenURL:authorizeURL
                                  accessTokenURL:accessURL
                                  authentication:auth
                                  appServiceName:keychainAppServiceName
                                      delegate:self
                                  finishedSelector:@selector(viewController:finishedWithAuth:error:)] autorelease];
      
      
      [[self navigationController] pushViewController:viewController animated:YES];

    }
    else {
      // Authentication succeeded
      
      // save the authentication object, which holds the auth tokens
      [self setAuthentication:auth];
      
      if (signupSocialNetworkType == kSignupSocialLinkedIn) {
        [self doAnAuthenticatedAPIFetchLinkedIn];
      }
      if (signupSocialNetworkType == kSignupSocialTwitter) {
        [self doAnAuthenticatedAPIFetchTwitter];
      }
      
    }
    
  }
}