You can retrieve a list of participants who are currently online and receiving all messages from an open channel using the
createParticipantListQuery() method. To retrieve a list of members in a group channel, call the
Members of a group channel are automatically updated when a user is online. But when a user is disconnected from the Sendbird server and then reconnected, you should call the
refresh(completionHandler:) method to update their channels with the latest information. See the refresh all data related to a group channel section for the sample code.