private_business_updates.ex

defmodule Jeangrey.PrivateBusinessUpdatesChannel do
  use Jeangrey.Web, :channel
  alias Jeangrey.Presence # <- Added this alias
  
  def join("private-business-updates:" <> id....) do
    # Existing code to authorize connection omitted...
    ....
    send(self, :after_join) # <- Added this
    {:ok, socket}
    ....
  end
  
  # New function
  def handle_info(:after_join, socket) do
    push socket, "presence_state", Presence.list(socket)
    {:ok, _} = Presence.track(socket, socket.assigns.user_id, %{
      online_at: inspect(System.system_time(:seconds))
      })
    {:noreply, socket}
  end
end