Use Notification Hubs to send breaking news

This topic shows you how to use Azure Notification Hubs to broadcast breaking news notifications to an iOS app. When complete, you will be able to register for breaking news categories you are interested in, and receive only push notifications for those categories. This scenario is a common pattern for many apps where notifications have to be sent to groups of users that have previously declared interest in them, e.g. RSS reader, apps for music fans, etc.

Broadcast scenarios are enabled by including one or more tags when creating a registration in the notification hub. When notifications are sent to a tag, all devices that have registered for the tag will receive the notification. Because tags are simply strings, they do not have to be provisioned in advance. For more information about tags, refer to Notification Hubs Guidance.

This tutorial walks you through these basic steps to enable this scenario:

1. Add category selection to the app
2. Register for notifications
3. Send notifications from your back-end
4. Run the app and generate notifications

This topic builds on the app you created in Get started with Notification Hubs. Before starting this tutorial, you must have already completed Get started with Notification Hubs.

Add category selection to the app

The first step is to add the UI elements to your existing storyboard that enable the user to select categories to register. The categories selected by a user are stored on the device. When the app starts, a device registration is created in your notification hub with the selected categories as tags.

1. In your MainStoryboard_iPhone.storyboard add the following components from the object library:
   • A label with "Breaking News" text,
   • Labels with category texts "World", "Politics", "Business", "Technology", "Science", "Sports",
   • Six switches, one per category,
   • On button labeled "Subscribe"
   Your storyboard should look as follows:
   
2. In the assistant editor, create outlets for all the switches and call them "WorldSwitch", "PoliticsSwitch", "BusinessSwitch", "TechnologySwitch", "ScienceSwitch", "SportsSwitch"
   
3. Create an Action for your button called "subscribe". Your BreakingNewsViewController.h should contain the following:

   @property (weak, nonatomic) IBOutlet UISwitch *WorldSwitch;
   @property (weak, nonatomic) IBOutlet UISwitch *PoliticsSwitch;
   @property (weak, nonatomic) IBOutlet UISwitch *BusinessSwitch;
   @property (weak, nonatomic) IBOutlet UISwitch *TechnologySwitch;
   @property (weak, nonatomic) IBOutlet UISwitch *ScienceSwitch;
   @property (weak, nonatomic) IBOutlet UISwitch *SportsSwitch;
   
   - (IBAction)subscribe:(id)sender;

4. Create a new class called Notifications. Copy the following code in the interface section of the file Notifications.h:

   @property NSData* deviceToken;
   
   - (void)storeCategoriesAndSubscribeWithCategories:(NSArray*) categories completion: (void (^)(NSError* error))completion;
   - (void)subscribeWithCategories:(NSSet*) categories completion:(void (^)(NSError *))completion;

5. Add the following import directive to Notifications.m:

   #import <WindowsAzureMessaging/WindowsAzureMessaging.h>

6. Copy the following code in the implementation section of the file Notifications.m:

   - (void)storeCategoriesAndSubscribeWithCategories:(NSSet *)categories completion:(void (^)(NSError *))completion {
       NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
       [defaults setValue:[categories allObjects] forKey:@"BreakingNewsCategories"];
   
       [self subscribeWithCategories:categories completion:completion];
   }
   
   - (void)subscribeWithCategories:(NSSet *)categories completion:(void (^)(NSError *))completion{
       SBNotificationHub* hub = [[SBNotificationHub alloc] initWithConnectionString:@"<connection string with listen access>" notificationHubPath:@"<hub name>"];
   
       [hub registerNativeWithDeviceToken:self.deviceToken tags:categories completion: completion];
   }

   This class uses local storage to store the categories of news that this device has to receive. Also, it contains methods to register these categories.
7. In the above code, replace the <hub name> and <connection string with listen access> placeholders with your notification hub name and the connection string for DefaultListenSharedAccessSignature that you obtained earlier.
   NOTE
   

   Because credentials that are distributed with a client app are not generally secure, you should only distribute the key for listen access with your client app. Listen access enables your app to register for notifications, but existing registrations cannot be modified and notifications cannot be sent. The full access key is used in a secured backend service for sending notifications and changing existing registrations.
8. In the BreakingNewsAppDelegate.h file, add the following property:

   @property (nonatomic) Notifications* notifications;

   This creates a singleton instance of the Notification class in the AppDelegate.
9. In the didFinishLaunchingWithOptions method in BreakingNewsAppDelegate.m, add the following code beforeregisterForRemoteNotificationTypes:

   self.notifications = [[Notifications alloc] init];

   The initializes the Notification singleton.
10. In the didRegisterForRemoteNotificationsWithDeviceToken method in BreakingNewsAppDelegate.m, remove the call toregisterNativeWithDeviceToken and add the following code:

    self.notifications.deviceToken = deviceToken;

    Note that at this point there should be no other code in the didRegisterForRemoteNotificationsWithDeviceTokenmethod.
11. Add the following method in BreakingNewsAppDelegate.m:

    - (void)application:(UIApplication *)application didReceiveRemoteNotification:
        (NSDictionary *)userInfo {
        NSLog(@"%@", userInfo);
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Notification" message:
        [[userInfo objectForKey:@"aps"] valueForKey:@"alert"] delegate:nil cancelButtonTitle: @"OK" otherButtonTitles:nil, nil];
        [alert show];
    }

    This method handles notifications received when the app is running by displaying a simple UIAlert.
12. In BreakingNewsViewController.m, copy the following code into the XCode-generated subscribe method:

    NSMutableArray* categories = [[NSMutableArray alloc] init];
    
    if (self.WorldSwitch.isOn) [categories addObject:@"World"];
    if (self.PoliticsSwitch.isOn) [categories addObject:@"Politics"];
    if (self.BusinessSwitch.isOn) [categories addObject:@"Business"];
    if (self.TechnologySwitch.isOn) [categories addObject:@"Technology"];
    if (self.ScienceSwitch.isOn) [categories addObject:@"Science"];
    if (self.SportsSwitch.isOn) [categories addObject:@"Sports"];
    
    Notifications* notifications = [(BreakingNewsAppDelegate*)[[UIApplication sharedApplication]delegate] notifications];
    
    [notifications storeCategoriesAndSubscribeWithCategories:categories completion: ^(NSError* error) {
        if (!error) {
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Notification" message:
                                  @"Subscribed!" delegate:nil cancelButtonTitle:
                                  @"OK" otherButtonTitles:nil, nil];
            [alert show];
        } else {
            NSLog(@"Error subscribing: %@", error);
        }
    }];

    This method creates an NSMutableArray of categories and uses the Notifications class to store the list in the local storage and registers the corresponding tags with your notification hub. When categories are changed, the registration is recreated with the new categories.

Your app is now able to store a set of categories in local storage on the device and register with the notification hub whenever the user changes the selection of categories.

Register for notifications

These steps register with the notification hub on startup using the categories that have been stored in local storage.

NOTE

Because the device token assigned by the Apple Push Notification Service (APNS) can chance at any time, you should register for notifications frequently to avoid notification failures. This example registers for notification every time that the app starts. For apps that are run frequently, more than once a day, you can probably skip registration to preserve bandwidth if less than a day has passed since the previous registration.

1. Add the following method in the interface section of the file Notifications.h:

   - (NSSet*)retrieveCategories;

   This code retrieves the categories in the Notifications class.
2. Add the corresponding implementation in the file Notifications.m:

   - (NSSet*)retrieveCategories {
       NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   
       NSArray* categories = [defaults stringArrayForKey:@"BreakingNewsCategories"];
   
       if (!categories) return [[NSSet alloc] init];
       return [[NSSet alloc] initWithArray:categories];
   }

3. Add the following code in the didRegisterForRemoteNotificationsWithDeviceToken method:

   Notifications* notifications = [(BreakingNewsAppDelegate*)[[UIApplication sharedApplication]delegate] notifications];
   
   NSSet* categories = [notifications retrieveCategories];
   [notifications subscribeWithCategories:categories completion:^(NSError* error) {
       if (error != nil) {
           NSLog(@"Error registering for notifications: %@", error);
       }
   }];

   This makes sure that every time the app starts it retrieves the categories from local storage and requests a registeration for these categories.
4. In BreakingNewsViewController.h, add the following code in the viewDidLoad method:

   Notifications* notifications = [(BreakingNewsAppDelegate*)[[UIApplication sharedApplication]delegate] notifications];
   
   NSSet* categories = [notifications retrieveCategories];
   
   if ([categories containsObject:@"World"]) self.WorldSwitch.on = true;
   if ([categories containsObject:@"Politics"]) self.PoliticsSwitch.on = true;
   if ([categories containsObject:@"Business"]) self.BusinessSwitch.on = true;
   if ([categories containsObject:@"Technology"]) self.TechnologySwitch.on = true;
   if ([categories containsObject:@"Science"]) self.ScienceSwitch.on = true;
   if ([categories containsObject:@"Sports"]) self.SportsSwitch.on = true;

   This updates the UI on startup based on the status of previously saved categories.

The app is now complete and can store a set of categories in the device local storage used to register with the notification hub whenever the user changes the selection of categories. Next, you will define a backend that can send category notifications to this app.

Send notificationsSend notifications from your back-end

This section shows how to send notifications from a .NET console app and any other. If you are using Mobile Services please refer to the Get Started with Push tutorials. If you want to use Java or PHP refer to How to use Notification Hubs from Java/PHP. You can send notifications from any backend using the Notification Hubs REST interface.

The following code sends notifications to Windows Store, Windows Phone, iOS, and Android devices.

Skip steps 1-3 if you created a console app when you completed Get started with Notification Hubs.

1. In Visual Studio create a new Visual C# console application:
   
2. In the Visual Studio main menu, click Tools, Library Package Manager, and Package Manager Console, then in the console window type the following and press Enter:

   Install-Package WindowsAzure.ServiceBus

   This adds a reference to the Azure Service Bus SDK by using the WindowsAzure.ServiceBus NuGet package.
3. Open the file Program.cs and add the following using statement:

   using Microsoft.ServiceBus.Notifications;

4. In the Program class, add the following method, or replace it if it already exists:

   private static async void SendNotificationAsync()
   {
       // Define the notification hub.
       NotificationHubClient hub = 
           NotificationHubClient.CreateClientFromConnectionString(
               "<connection string with full access>", "<hub name>");
   
       // Create an array of breaking news categories.
       var categories = new string[] { "World", "Politics", "Business", 
           "Technology", "Science", "Sports"};
   
       foreach (var category in categories)
       {
           try
           {
               // Define a Windows Store toast.
               var wnsToast = "<toast><visual><binding template=\"ToastText01\">" 
                   + "<text id=\"1\">Breaking " + category + " News!" 
                   + "</text></binding></visual></toast>";         
               await hub.SendWindowsNativeNotificationAsync(wnsToast, category);
   
               // Define a Windows Phone toast.
               var mpnsToast =
                   "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                   "<wp:Notification xmlns:wp=\"WPNotification\">" +
                       "<wp:Toast>" +
                           "<wp:Text1>Breaking " + category + " News!</wp:Text1>" +
                       "</wp:Toast> " +
                   "</wp:Notification>";         
               await hub.SendMpnsNativeNotificationAsync(mpnsToast, category);
   
               // Define an iOS alert.
               var alert = "{\"aps\":{\"alert\":\"Breaking " + category + " News!\"}}";
               await hub.SendAppleNativeNotificationAsync(alert, category);
   
               // Define an Android notification.
               var notification = "{\"data\":{\"msg\":\"Breaking " + category + " News!\"}}";
               await hub.SendGcmNativeNotificationAsync(notification, category);
           }
           catch (ArgumentException)
           {
               // An exception is raised when the notification hub hasn't been 
               // registered for the iOS, Windows Store, or Windows Phone platform. 
           }
       }
    }

   This code sends notifications for each of the six tags in the string array to Windows Store, Windows Phone and iOS devices. The use of tags makes sure that devices receive notifications only for the registered categories.
   NOTE
   

   This backend code supports Windows Store, Windows Phone, iOS, and Android clients. Send methods return an error response when the notification hub hasn't yet been configured for a particular client platform.
5. In the above code, replace the <hub name> and <connection string with full access> placeholders with your notification hub name and the connection string for DefaultFullSharedAccessSignature that you obtained earlier.
6. Add the following lines in the Main method:

    SendNotificationAsync();
    Console.ReadLine();

Run the app and generate notifications

1. Press the Run button to build the project and start the app.
   
   Note that the app UI provides a set of toggles that lets you choose the categories to subscribe to.
2. Enable one or more categories toggles, then click Subscribe.
   When you choose Subscribe, the app converts the selected categories into tags and requests a new device registration for the selected tags from the notification hub.
3. Send a new notification from the backend in one of the following ways:
   • Console app: start the console app.
   • Java/PHP: run your app/script.
4. Notifications for the selected categories appear as toast notifications.

Source from

http://azure.microsoft.com/en-us/documentation/articles/notification-hubs-ios-send-breaking-news/