Initializes a new message that is part of the provided session.
- iOS 10.0+
The session object tracking an updatable exchange of messages.
A newly initialized message.
Use this initializer to create an updatable message. Messages that are part of a session receive special treatment by the Messages app. When the app receives a message that is part of an existing session, the previous message is moved to the bottom of the transcript and updated with the new message’s content.