Add simpler delegate method for FCM tokens (#375)

This new delegate method will be called generally once per app start, to always provide a current token. This token may change over time. This simpler method makes integration much simpler, as:

* Developers no longer have to check for a current token using the `.fcmToken` property, and also check for token changes using the `-messaging:didRefreshRegistrationToken:` delegate method.
* There is a single code path for when a token is available, making operations that depend on a token being available easier to implement. For example, this is the right method to always upload your FCM token to your application server, or to subscribe to topics, etc.

1 files changed, 9 insertions, 12 deletions

diff --git a/Example/Messaging/App/iOS/AppDelegate.swift b/Example/Messaging/App/iOS/AppDelegate.swift
index aafd844..32b55ed 100644
--- a/Example/Messaging/App/iOS/AppDelegate.swift
+++ b/Example/Messaging/App/iOS/AppDelegate.swift
@@ -66,19 +66,9 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
       // register for remote notifications
       NotificationsController.shared.registerForUserFacingNotificationsFor(application)
     }
-
-    printFCMToken()
     return true
   }
 
-  func printFCMToken() {
-    if let token = Messaging.messaging().fcmToken {
-      print("FCM Token: \(token)")
-    } else {
-      print("FCM Token: nil")
-    }
-  }
-
   func application(_ application: UIApplication,
                    didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
     print("APNS Token: \(deviceToken.hexByteString)")
@@ -116,8 +106,15 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 }
 
 extension AppDelegate: MessagingDelegate {
-  func messaging(_ messaging: Messaging, didRefreshRegistrationToken fcmToken: String) {
-    printFCMToken()
+  // FCM tokens are always provided here. It is called generally during app start, but may be called
+  // more than once, if the token is invalidated or updated. This is the right spot to upload this
+  // token to your application server, or to subscribe to any topics.
+  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
+    if let token = Messaging.messaging().fcmToken {
+      print("FCM Token: \(token)")
+    } else {
+      print("FCM Token: nil")
+    }
   }
 
   // Direct channel data messages are delivered here, on iOS 10.0+.