Settings View Source Using Gettext for internationalization

For internationalization with gettext, the locale used within your Plug pipeline can be stored in the Plug session and restored within your LiveView mount. For example, after user signs in or preference changes, you can write the locale to the session:

def put_user_session(conn, current_user) do
  locale = get_locale_for_user(current_user)
  Gettext.put_locale(MyApp.Gettext, locale)

  conn
  |> put_session(:user_id, current_user.id)
  |> put_session(:locale, locale)
end

Then in your LiveView mount/3, you can restore the locale:

def mount(_params, %{"locale" => locale}, socket) do
  Gettext.put_locale(MyApp.Gettext, locale)
  {:ok, socket}
end

You can also use the on_mount (Phoenix.LiveView.on_mount/1) hook to automatically restore the locale for every LiveView in your application:

defmodule MyAppWeb.RestoreLocale do
  def on_mount(:default, _params, %{"locale" => locale} = _session, socket) do
    Gettext.put_locale(MyApp.Gettext, locale)
    {:cont, socket}
  end

  # for any logged out routes
  def on_mount(:default, _params, _session, socket), do: {:cont, socket}
end

Then, add this hook to def live_view under MyAppWeb, to run it on all LiveViews by default:

def live_view do
  quote do
    use Phoenix.LiveView,
      layout: {MyAppWeb.LayoutView, :live}

    on_mount MyAppWeb.RestoreLocale
    unquote(view_helpers())
  end
end