Receive messages in an iOS app

Once your client app is installed on a device, it can receive messages through the FCM APNs interface. You can immediately start sending notifications to user segments with the Notifications composer, or your application server can send messages with a notification payload through the APNs interface.

Handling messages received through the FCM APNs interface is likely to cover most typical use cases. For special use cases demanding very high reliability, you can handle direct FCM channel message in your app. You can also send upstream messages.

Handle messages received through the FCM APNs interface

When your app is in the background, iOS directs messages with the notification key to the system tray. A tap on a notification opens the app, and the content of the notification is passed to the didReceiveRemoteNotification callback in the AppDelegate.

Implement AppDelegate application:didReceiveRemoteNotification: as shown:

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any]) {
  // If you are receiving a notification message while your app is in the background,
  // this callback will not be fired till the user taps on the notification launching the application.
  // TODO: Handle data of notification

  // With swizzling disabled you must let Messaging know about the message, for Analytics
  // Messaging.messaging().appDidReceiveMessage(userInfo)

  // Print message ID.
  if let messageID = userInfo[gcmMessageIDKey] {
    print("Message ID: \(messageID)")
  }

  // Print full message.
  print(userInfo)
}

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
                 fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
  // If you are receiving a notification message while your app is in the background,
  // this callback will not be fired till the user taps on the notification launching the application.
  // TODO: Handle data of notification

  // With swizzling disabled you must let Messaging know about the message, for Analytics
  // Messaging.messaging().appDidReceiveMessage(userInfo)

  // Print message ID.
  if let messageID = userInfo[gcmMessageIDKey] {
    print("Message ID: \(messageID)")
  }

  // Print full message.
  print(userInfo)

  completionHandler(UIBackgroundFetchResult.newData)
}

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo {
  // If you are receiving a notification message while your app is in the background,
  // this callback will not be fired till the user taps on the notification launching the application.
  // TODO: Handle data of notification

  // With swizzling disabled you must let Messaging know about the message, for Analytics
  // [[FIRMessaging messaging] appDidReceiveMessage:userInfo];

  // Print message ID.
  if (userInfo[kGCMMessageIDKey]) {
    NSLog(@"Message ID: %@", userInfo[kGCMMessageIDKey]);
  }

  // Print full message.
  NSLog(@"%@", userInfo);
}

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
    fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
  // If you are receiving a notification message while your app is in the background,
  // this callback will not be fired till the user taps on the notification launching the application.
  // TODO: Handle data of notification

  // With swizzling disabled you must let Messaging know about the message, for Analytics
  // [[FIRMessaging messaging] appDidReceiveMessage:userInfo];

  // Print message ID.
  if (userInfo[kGCMMessageIDKey]) {
    NSLog(@"Message ID: %@", userInfo[kGCMMessageIDKey]);
  }

  // Print full message.
  NSLog(@"%@", userInfo);

  completionHandler(UIBackgroundFetchResultNewData);
}

If you want to open your app and perform a specific action, set click_action in the notification payload. Use the value that you would use for the category key in the APNs payload.

Interpreting notification message payload

The payload of notification messages is a dictionary of keys and values. Notification messages sent through APNs follow the APNs payload format as below:

  {
    "aps" : {
      "alert" : {
        "body" : "great match!",
        "title" : "Portugal vs. Denmark",
      },
      "badge" : 1,
    },
    "customKey" : "customValue"
  }

Handle messages with method swizzling disabled

If you disable method swizzling, you'll need to call a method to let FCM track message delivery and analytics. This is performed automatically with method swizzling enabled.

In iOS 10 and above, you can set the UNUserNotificationCenter delegate to receive display notifications from Apple and FIRMessaging's delegate property to receive data messages from FCM. If you do not set these two delegates with AppDelegate, method swizzling for message handling is disabled. You'll need to call appDidReceiveMessage: to track message delivery and analytics.

// Receive displayed notifications for iOS 10 devices.
// Handle incoming notification messages while app is in the foreground.
- (void)userNotificationCenter:(UNUserNotificationCenter *)center
       willPresentNotification:(UNNotification *)notification
         withCompletionHandler:(void (^)(UNNotificationPresentationOptions))completionHandler {
  NSDictionary *userInfo = notification.request.content.userInfo;

  // With swizzling disabled you must let Messaging know about the message, for Analytics
  // [[FIRMessaging messaging] appDidReceiveMessage:userInfo];

  // Print message ID.
  if (userInfo[kGCMMessageIDKey]) {
    NSLog(@"Message ID: %@", userInfo[kGCMMessageIDKey]);
  }

  // Print full message.
  NSLog(@"%@", userInfo);

  // Change this to your preferred presentation option
  completionHandler(UNNotificationPresentationOptionNone);
}

// Handle notification messages after display notification is tapped by the user.
- (void)userNotificationCenter:(UNUserNotificationCenter *)center
didReceiveNotificationResponse:(UNNotificationResponse *)response
         withCompletionHandler:(void(^)(void))completionHandler {
  NSDictionary *userInfo = response.notification.request.content.userInfo;
  if (userInfo[kGCMMessageIDKey]) {
    NSLog(@"Message ID: %@", userInfo[kGCMMessageIDKey]);
  }

  // Print full message.
  NSLog(@"%@", userInfo);

  completionHandler();
}

// With "FirebaseAppDelegateProxyEnabled": NO
   - (void)application:(UIApplication *)application
     didReceiveRemoteNotification:(NSDictionary *)userInfo
           fetchCompletionHandler:
               (void (^)(UIBackgroundFetchResult))completionHandler {
   // Let FCM know about the message for analytics etc.
   [[FIRMessaging messaging] appDidReceiveMessage:userInfo];
   // handle your message.
 }
 

@available(iOS 10, *)
extension AppDelegate : UNUserNotificationCenterDelegate {

  // Receive displayed notifications for iOS 10 devices.
  func userNotificationCenter(_ center: UNUserNotificationCenter,
                              willPresent notification: UNNotification,
    withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
    let userInfo = notification.request.content.userInfo

    // With swizzling disabled you must let Messaging know about the message, for Analytics
    // Messaging.messaging().appDidReceiveMessage(userInfo)

    // Print message ID.
    if let messageID = userInfo[gcmMessageIDKey] {
      print("Message ID: \(messageID)")
    }

    // Print full message.
    print(userInfo)

    // Change this to your preferred presentation option
    completionHandler([])
  }

  func userNotificationCenter(_ center: UNUserNotificationCenter,
                              didReceive response: UNNotificationResponse,
                              withCompletionHandler completionHandler: @escaping () -> Void) {
    let userInfo = response.notification.request.content.userInfo
    // Print message ID.
    if let messageID = userInfo[gcmMessageIDKey] {
      print("Message ID: \(messageID)")
    }

    // Print full message.
    print(userInfo)

    completionHandler()
  }
}

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
     // Let FCM know about the message for analytics etc.
     FIRMessaging.messaging().appDidReceiveMessage(userInfo)
     // handle your message
   }
 

Handle direct FCM channel messages

To reliably receive silent, data-only messages directly from FCM, bypassing APNs when the app is in the foreground, you'll need to connect to the FCM service and handle messages with FIRMessagingDelegate's messaging:didReceiveMessage: method. With the direct channel enabled, the FCM backend uses a reliable message queue to keep track of pending messages when the app is in the background or closed. When the app goes to the foreground and the connection is re-established, the channel will automatically send pending messages to the client until it gets an acknowledgement from the client.

To connect, set the shouldEstablishDirectChannel flag to YES in the AppDelegate. FCM manages the connection, closing it when your app goes into the background and reopening it whenever the app is foregrounded.

Also, set the useMessagingDelegateForDirectChannel flag to YES in the AppDelegate and implement messaging:didReceiveMessage:. Your app can still receive APNs messages with or without this callback, but for direct messages from FCM you'll need it.

Interpreting data message payload

The payload of data messages is a dictionary of keys and values. Data messages sent to the devices directly by FCM server are expressed in the format of a dictionary as below：

  {
    "body" : "great match!",
    "title" : "Portugal vs. Denmark",
    "icon" : "myicon"
  }

Handle queued and deleted messages

Apps that connect to FCM to receive data messages should handle FIRMessagingMessagesDeletedNotification. You may receive this callback when there are too many messages (>100) pending for your app on a particular device at the time it connects, or if the device hasn't connected to FCM for more than one month. When the app instance receives this callback, it should perform a full sync with your app server.

For insight into message delivery to your app, see the FCM reporting dashboard, which records the number of messages sent and opened on iOS and Android devices, along with data for "impressions" (notifications seen by users) for Android apps.