This is s proof-of-concept demonstrator for the new Group Activities for FaceTime available with iOS 15. It's an extension of my MultipeerPuppies proof-of-concept demonstrator.

Here's a link to video of an early version.

The talk at WWDC2021 that got me started playing with Group Activities. It includes a demo and parts of the code for a shared whiteboard app.

Thanks to @_inside for tweeting this and getting me off my duff. I spent an afternoon making this work.

This is the SharePlay introduction video.

This talk has useful tidbits for starting the session, even if your application has nothing to do with media.

This talk also has useful tidbits.

This object will tell you if a FaceTime call is in progress. Its observable boolean member variable, isElegibleForGroupSession turns true if you have a connection.

GroupActivity is a protocol to define the topic for the session. The session is tied to a particular activity.

I don't know if an application may have multiple types of sessions going at one time. It is at least possible. An activity type is necessary but not suffient to identify a session. Two different apps using the same activityIdentifier will not connect.

This is the source and sink for messages in the session. Create it, passing the session object, when you get a new or modified session.

This class distills what I currently know about GroupActivities.

• It will handle sessions for one activity.
• It will send and receive messages so long as they conform to the GroupActivityMessage protocol, which adds requirements for a UUID based identifier and a timestamp to the base requirement that messages conform to Codable. This way the handler can tell if a message is older than the most recent one received.
• I tried to remove any app specific logic from it.
• It provides a delegate based interface to GroupActivities

I still don't understand the session life cycle. I don't know what backgrounding and foregrounding the app actually does to a session, or how to recover from it.