Broadcast multiple topics at once

romaluca · May 30, 2017, 1:08pm

Hi, i have 2 models: album, photo and 2 type topics: album:#{id} and photo:#{id}

The user when open an album page joins to album:#{id} topic and when open a photo page joins to photo:#{id} topic.
In both page it is possible to vote the photos.

So when the user vote i have to broadcast the vote to both topics.

What is the best method for do this?

Thanks

outlog · May 30, 2017, 2:15pm

depends on how you receive the vote (in a controller or in a channel) both cases are documented here:

github.com

phoenixframework/phoenix/blob/v1.2.4/lib/phoenix/channel.ex#L130




    # do not send broadcasted `"user_joined"` events if this socket's user
    # is ignoring the user who joined.
    def handle_out("user_joined", msg, socket) do
      unless User.ignoring?(socket.assigns[:user], msg.user_id) do
        push socket, "user_joined", msg
      end
      {:noreply, socket}
    end


## Broadcasting to an external topic


In some cases, you will want to broadcast messages without the context of
a `socket`. This could be for broadcasting from within your channel to an
external topic, or broadcasting from elsewhere in your application like a
controller or another process. Such can be done via your endpoint:


    # within channel
    def handle_in("new_msg", %{"uid" => uid, "body" => body}, socket) do
      ...
      broadcast_from! socket, "new_msg", %{uid: uid, body: body}