Phoenix Presence of docs does not work for me

I pretty much followed the docs about phoenix presence, but I cannot get it working in the UI. It works in the Elixir Code, but the info is never brought to the template.

Specifically, the onSync-Call seems never to be executed regardless the join of a new user :

presence.onSync(() => showOnlineStatus(presence))

If I do it manually as stated in the generated presence.ex via

chatChannel.on("presence_diff", diff => {

it calls the showOnlineStatus() function. Nevertheless,

presence.list((name, { metas: [first,] }) => { ... })

never executes anything, even though presence contains the diff information.

The full code can be found in the Github repo.

What I am doing wrong? Do I miss anything what the docs requires me to do but isn’t stated? Are the docs missing anything?


I’m not sure if this is the issue but it looks like you are executing Presence.track inside handle_in instead of a handle_info:

Maybe it’ll work if you use send(self(), :after_join), here’s an example from the Phoenix.Presence docs:

  def join("some:topic", _params, socket) do
    send(self(), :after_join)
    {:ok, assign(socket, :user_id, ...)}

  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(:second))
    {:noreply, socket}
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Does not matter where it’s executed. I had it initially in a handle_info but it also didn’t work.

If I follow this guide it works anyway. I still wonder, why the solution of the docs does not work.

That guide is for an older version of Phoenix. Have you seen something that works with 1.4?

Same exact issue for me, did anyone figure this out?

It might be for an older version but the guide definitely works for me with 1.4

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I figured out my problem but I cannot tell why I did that mistake, maybe the docs weren’t right at that time.

push socket, "online", Presence.list(socket)

was the problem. "online" needs to match the callbacks you’re listening on with Javascript so there should have been "presence_state" instead.

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