Update the iOS documentation on how to manage the badge (#409)

* Update the iOS documentation on how to manage the badge

* Update docs/delivery_methods/ios.md

* Simplify example

---------

Co-authored-by: Chris Oliver <[email protected]>

docs/delivery_methods/ios.md

@@ -19,7 +19,7 @@ https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_
 ## Usage
 
 ```ruby
-class CommentNotification
+class CommentNotifier < ApplicationNotifier
  deliver_by :ios do |config|
  config.device_tokens = -> { recipient.notification_tokens.where(platform: :iOS).pluck(:token) }
  config.format = ->(apn) {
@@ -83,13 +83,54 @@ end
 Apple Push Notifications may fail delivery if the user has removed the app from their device. Noticed allows you
 
 ```ruby
-class CommentNotification
+class CommentNotifier < ApplicationNotifier
  deliver_by :ios do |config|
  config.invalid_token = ->(token) { NotificationToken.where(token: token).destroy_all }
  end
 end
 ```
 
+## Updating the iOS app badge
+
+If you're managing the iOS app badge, you can pass it along in the format
+
+```ruby
+class CommentNotifier < ApplicationNotifier
+ deliver_by :ios do |config|
+ config.format = ->(apn) {
+ apn.alert = "Hello world"
+ apn.custom_payload = {url: root_url(host: "example.org")}
+ apn.badge = recipient.notifications.unread.count
+ }
+ end
+end
+```
+
+Another common action is to update the badge after a user reads a notification. 
+
+This is a great use of the Noticed::Ephemeral class. Since it's all in-memory, it will perform the job and not touch the database.
+
+```ruby
+class NativeBadgeNotifier < Noticed::Ephemeral
+ deliver_by :ios do |config|
+ config.format = ->(apn) {
+ # Setting the alert text to nil will deliver the notification in
+ # the background. This is used to update the app badge on the iOS home screen
+ apn.alert = nil
+ apn.custom_payload = {}
+ apn.badge = recipient.notifications.unread.count
+ }
+ end
+end
+```
+
+Then you can simply deliver this notifier to update the badge when you mark the notification as read
+
+```ruby
+notification.mark_as_read!
+NativeBadgeNotifier.with(record: notification).deliver(notification.recipient)
+```
+
 ## Delivering to Sandboxes and real devices
 
 If you wish to send notifications to both sandboxed and real devices from the same application, you can configure two iOS delivery methods