CODEWITHSUNDEEP
websocketelixirphoenix-framework
Aaron Dufall
Aaron Dufall

Reputation: 1177

Phoenix: Only allow subscription to one sub topic on a channel at a time

If a user has joined a topic, say "rooms:lobby" and then the user joins another sub topic on the same channel, like "rooms:party". How can I force the user to be leave "rooms:lobby" from the backend. I have tried filtering the broadcast, but haven't had any luck. I would prefer to just terminate connection to old sub topics over filtering broadcasts.

defmodule MyApp.RoomsChannel do
  use Phoenix.Channel
  intercept ["new_msg"]

  def join("rooms:" <> room_id, _params, socket) do
    {:ok, assign(socket, :room_id, room_id)
  end

  def handle_out("new_msg", payload, socket) do
    if current_room?(socket.assigns[:room_id], socket.topic) do
      push socket, "new_msg", payload
      {:noreply,socket}
    else
      {:noreply, socket}
    end
  end

  defp current_room?(room_id, "rooms:" <> sub_topic) do
    room_id == sub_topic
  end
end

I know it's possible to leave a topic from the front-end, but I need to ensure that only they current topic they are viewing gets the payload and not any of the previous topics that where subscribed to on a particular channel.

Upvotes: 3

Views: 1270

Answers (1)

Jeff Levy
Jeff Levy

Reputation: 26

From your comments it sounds like you are trying to join 1 channel per route, and you want to switch channels when the route changes instead of accumulating multiple channels. My guess is you are joining the channel inside of a lifecycle method (e.g. ComponentWillMount) from a high level React component.

If so, why not terminate the channel from the client in ComponentWillUnmount? This should fire just before your route changes on the client.

Upvotes: 1

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