A type alias representing a Presence on a Channel.

• id - The id used to identify the Presence map in the Presence.track/3 Elixir function. The recommended approach is to use the users' id.

• metas- A list of metadata as stored in the Presence.track/3 Elixir function.

• user - The user data that is pulled from the DB and stored on the Presence in the fetch/2 Elixir callback function. This is the recommended approach for storing user data on the Presence. If fetch/2 is not being used then user will be equal to Json.Encode.null.

• presence - The whole Presence map. This provides a way to access any additional data that is stored on the Presence.

-- MyAppWeb.MyChannel.ex

def handle_info(:after_join, socket) do
  {:ok, _} = Presence.track(socket, socket.assigns.user_id, %{
    online_at: System.os_time(:millisecond)
  })

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

  {:noreply, socket}
end

-- MyAppWeb.Presence.ex

defmodule MyAppWeb.Presence do
  use Phoenix.Presence,
    otp_app: :my_app,
    pubsub_server: MyApp.PubSub

  def fetch(_topic, presences) do
    query =
      from u in User,
      where: u.id in ^Map.keys(presences),
      select: {u.id, u}

    users = query |> Repo.all() |> Enum.into(%{})

    for {key, %{metas: metas}} <- presences, into: %{} do
      {key, %{metas: metas, user: users[key]}}
    end
  end
end

A type alias representing the joins and leaves on the Channel as they happen.

A type alias representing the Channel topic id. For example "topic:subTopic".

An InternalError should never happen, but if it does, it is because the JS is out of sync with this package.

If you ever receive this message, please raise an issue.

All of the Presence messages that can come from the Channel.

If you are using more than one Channel, then you can pattern match on Topic to determine which Channel the Msg relates to.

A type alias representing the port function required to receive a Msg from Phoenix Presence.

You will find this port function in the Port module.

Subscribe to receive incoming Presence Msgs.

import Phoenix.Presence as Presence
import Ports.Phoenix as Port


type Msg
  = PresenceMsg Presence.Msg
  | ...




subscriptions : Model -> Sub Msg
subscriptions _ =
    Presence.subscriptions
        PresenceMsg
        Port.presenceReceiver