Mark messages as read

To keep the most up-to-date and accurate read status of messages for all group channel members, the markAsRead(completionHandler:) method should be called every time a member reads messages by entering the channel from a channel list or switching the chat view from the background to the foreground.

When a member sends a message to the channel, the Sendbird server immediately updates the sender's read receipt to the time when the message was sent. The read receipts of other channel members are updated when the markAsRead(completionHandler:) method is called.

If a member opens a channel and the markAsReadAll(completionHandler:) is called, the Sendbird server updates both the unread message count of the individual channel and the total unread message count of all the group channels joined by the member. The server then triggers the channelDidUpdateReadStatus(_:) method of the channel event delegate to notify the change of read status to all other channel members' devices.

If a new member joins the channel, the method works differently based on the value of the display_past_message property of your Sendbird application. If the property is set to true, the new member's read receipt is updated to the sent time of the last message in the channel. If set to false, the property's value is 0.

// Call the markAsRead method when the current user views
// unread messages in a group channel.
channel.markAsRead { error in
    guard error == nil else {
        // Handle error.
        return
    }
}


// To listen to an update from other channel members' client apps,
// implement the `channelDidUpdateReadStatus(_:)` with actions to perform when notified.
class GroupChannelChattingViewController: UIViewController, GroupChannelDelegate {
    func initViewController() {
        SendbirdChat.add(self as GroupChannelDelegate, identifier: UNIQUE_DELEGATE_ID)
    }

    func channelDidUpdateReadStatus(_ channel: GroupChannel) {
        if currentGroupChannel.channelURL == channel.channelURL {
            // You can implement codes to redraw a channel view here.
        }
    }
}

Note: The display_past_message property determines whether to display past messages to newly joined members when they enter the channel. This property is also linked to the Chat history option, which can be managed on Sendbird Dashboard under Settings > Chat > Channels > Group channels.

Call the markAsUnread(message:completionHandler:) method to return a message's read status back to unread in a group channel. This is useful when users need to flag messages for later review or when they want to keep track of messages that they haven't read yet. This status change is only visible to the user who marked the message as unread, and it doesn't affect other users in the channel.

To mark messages as unread, call the markAsUnread() method on the GroupChannel object. You must specify a message that you want to mark as unread. This will be the starting point for the unread status. Messages after this are also treated as unread. Once marked, the SDK updates the unread message count of the group channel and triggers the channelDidUpdateReadStatus(_:) delegate method in the GroupChannelDelegate and didUpdateTotalUnreadMessageCount(unreadMessageCount:) delegate method in the UserEventDelegate.

In the meantime, the channelDidUpdateReadStatus(_:) delegate method of GroupChannelDelegate can also be implemented to listen to read status updates by other channel members.

groupChannel.markAsUnread(message) { error in 
  // Handle error if any.
}

// Listen to updates in the current user's `myLastRead` of the channel through the method below.
// Also use this to listen to a read status update by other channel members.
func channelDidUpdateReadStatus(_ channel: BaseChannel, userIds: [String]) {
    // ...
}

// Listen to updates in the current user's unread message count through the method below.
func didUpdateTotalUnreadMessageCount(unreadMessageCount:) {
    let totalUnreadCount = unreadMessageCount.groupChannelCount 
}

To get the read status of messages in a group channel, use the getReadStatus(with:) method. The method returns a list of objects with the user ID as the key and the read status as the value. The read status object contains the timestamp of the last message the user has seen.

// If with is false, the result won't include the current user.
let membersReadStatus = groupChannel.getReadStatus(with: false)
membersReadStatus.forEach { userId, readStatus in
    // Handle the read status of each member.
}