Какими методами можно обеспечить надежную доставку push-уведомлений пользователю?

To reliably deliver push notifications on iOS, the following methods can be used:

• Using APNs with delivery confirmation: Apple Push Notification service guarantees delivery to the device, but not that the user will see it. To increase reliability, track delivery status via feedback service or use notification extensions.

• Error handling and retries: The server should handle errors from APNs (e.g., device unavailable) and retry sending notifications if needed.

• Using local notifications as backup: If push notification is not delivered, the app can generate a local notification upon next launch.

• Synchronizing state via server: Instead of relying solely on push, the app can synchronize state with the server on launch or in background to get missed events.

• Using VoIP push (for VoIP apps): They have higher delivery priority.

Example of sending push on server (Python, simplified):

import apns2

client = apns2.APNsClient('cert.pem', use_sandbox=True)

notification = apns2.Notification(
    alert="New message",
    badge=1,
    sound="default"
)

try:
    client.send_notification('device_token', notification, topic='com.example.app')
except apns2.errors.ConnectionError:
    # Retry logic
    pass

This approach helps ensure notifications are received even with network issues.