AgoraVideoViewController.swift

@IBAction func didTapChat(_ sender: Any) {
    let storyboard = UIStoryboard(name: "ChatViewController", bundle: nil)
    let chatVC = storyboard.instantiateInitialViewController()!

    // Use the popover presentation style for your view controller.
    chatVC.modalPresentationStyle = .popover

    if let chatVC = chatVC as? ChatViewController {
        chatVC.channelName = channelName
        chatVC.agoraRtm = agoraRtm
    }

    // Present the view controller (in a popover).
    self.present(chatVC, animated: true) {

    }
}