Correct.

Well, I would do this:

• lib
  • my_app/weather
    • city.ex # schema
    • temperature.ex # schema
    • weather.ex # context
  • my_app_web/channels
    • user_socket.ex # socket
    • city_channel.ex # channel

Then in my_app_web/channels/user_socket.ex:

defmodule MyAppWeb.UserSocket do
  use Phoenix.Socket

  ## Channels
  channel "city:*", MyAppWeb.CityChannel

  # ...
end

And in my_app_web/channels/city_channel.ex:

defmodule MyAppWeb.DashboardChannel do
  use MyAppWeb, :channel

  alias MyApp.Weather

  def join("city:" <> id, _payload, socket) do
    {:ok, Socket.assign(socket, :city_id, id)}
  end

  def handle_in("update_temperature", params, socket) do
    case Weather.update_temperature(socket.assigns[:city_id], params) do
      {:ok, temperature} -> broadcast! socket, "update_temperature", %{body: temperature}
      {:error, cs} -> # handle your error
    end
    {:noreply, socket}
  end
end