Firebase FCM silent push notifications for iOS

Question

I have a problem with silent notifications on iOS.

When my application is in background, I don't receive silent notification sent by FCM. But if I try to send directly to APNS, the notification is successfully received.

This is the JSON sent to FCM:

{  "to" : "<token>", "priority": "high", "content_available": true, "data" : {   "<key>" : "<string>",   "<key2>" : "<string>" } 

}

This is the JSON sent directly to APNS:

{   "aps": {     "content-available": 1   },   "<key>": "<string>",   "<key>": "<string>" } 

I have already tried to remove the "priority" key because I saw someone saying that I shouldn't set the priority if the "content_available" is already set. It didn't work.

1. I have "Push Notifications" enabled in XCode > Capabilities.
2. I have "Remote notifications" checked in Background Modes in XCode > Capabilities.
3. The FCM notifications are working fine when app is in foreground and sometimes when the app is in background.

Answer 1

Remove "notification" key value pair and add "content_available": true

It will look like this

{      "to" : "...",     "priority": "high",     "content_available": true,     "data" : {       ....     } } 

This should make it a silent APNS and you need to handle with corresponding APNS delegate methods.

You will need to handle this through delegates Refer this firebase documentation for details: https://firebase.google.com/docs/cloud-messaging/concept-options

Answer 2

I found an workaround. I put an empty value for "sound" in "notification" field and the silent notifications are delivered even when the application is in background.

{      "to" : "...",     "priority": "high",     "notification": {         "sound": ""     },     "data" : {       ....     } } 

My hunch is that Apple does not allow silent notifications with a 'high' priority and somehow "notification": {"sound": ""} tricks the APNS that this notification is not a silent one.