title: Swift - remove all delivered notifications on all devices
body: <p>I've made a simple app, which is receiving push notifications from a service called OneSignal. This service just pushes notifications to devices without any user tracking, etc. so the user receives the notification on all devices, the app is installed. </p>
  
  <p>I was wondering if it's possible to clear all notifications in the notification center on all devices in swift, without any server side modifications, like sending a badge=0 push to all other devices? My goal is, that when the user taps the notification / opens the App on his iPhone, the notifications are cleared on his iPad or other iCloud-linked device too.</p>
  
  <p>This works unfortunately just locally and not on all devices of the same Apple ID:</p>
  
  <pre><code>application.applicationIconBadgeNumber = 0
  UNUserNotificationCenter.current().removeAllDeliveredNotifications()
  </code></pre>