app-service-mobile-ios-authenticate-app-with-token.md

The previous example contacts both the identity provider and the mobile service every time the app starts. Instead, you can cache the authorization token and try to use it first.

• The recommended way to encrypt and store authentication tokens on an iOS client is use the iOS Keychain. We'll use SSKeychain -- a simple wrapper around the iOS Keychain. Follow the instructions on the SSKeychain page and add it to your project. Verify that the Enable Modules setting is enabled in the project's Build Settings (section Apple LLVM - Languages - Modules.)

• Open QSTodoListViewController.m and add the following code:

		- (void) saveAuthInfo {
				[SSKeychain setPassword:self.todoService.client.currentUser.mobileServiceAuthenticationToken forService:@"AzureMobileServiceTutorial" account:self.todoService.client.currentUser.userId]
		}


		- (void)loadAuthInfo {
				NSString *userid = [[SSKeychain accountsForService:@"AzureMobileServiceTutorial"][0] valueForKey:@"acct"];
		    if (userid) {
		        NSLog(@"userid: %@", userid);
		        self.todoService.client.currentUser = [[MSUser alloc] initWithUserId:userid];
		         self.todoService.client.currentUser.mobileServiceAuthenticationToken = [SSKeychain passwordForService:@"AzureMobileServiceTutorial" account:userid];

		    }
		}

• In loginAndGetData, modify loginWithProvider:controller:animated:completion:'s completion block. Add the following line right before [self refresh] to store the user ID and token properties:

				[self saveAuthInfo];

• Let's load the user ID and token when the app starts. In the viewDidLoad in QSTodoListViewController.m, add this right afterself.todoService is initialized.

				[self loadAuthInfo];