Chat iOS v4
When a user is online, all data associated with the group channels they are a member of are automatically updated. However, when a user is disconnected from the Sendbird server and reconnects later, the
refresh(completionHandler:) method should be called to update the channels with the latest information.
Note: If you want to provide the updated channels with the latest information when your user's app is in the foreground, call
didSucceedReconnection()method which receives a callback from the Sendbird server when successfully reconnected.