iOS 10 How to set UNotificationContent threadIdentifier for remote notification

Question

TL;DR: What key needs to be set in the APNs notification payload JSON to correspond to the threadIdentifier property of the UNNotificatio

Answer 1

I discovered from a contact at Apple that the correct key to populate this property is the "thread-id" key.

So the JSON sent to APNs is as follows:

{
    "aps" : {
        "alert" : "Hello World!",
        "sound" : "default",
        "category" : "example-category",
        "thread-id" : "my conversation blah blah"
    }
    "custom-field" : "some value",
}

This populates the threadIdentifier property of the UNNotificationContent object accessible in your Notification Content Extension via notification.request.content.threadIdentifier.

By setting this "thread-id" value, it means that the didReceive(_:) method of your content extension will be multiple times. First when expanding the notification initially, and again whenever a new notification arrives with the same "thread-id" value.

I assume (hope) this will be added to the official documentation once iOS 10 is officially released.