The Arc commands and queries, called in-process from a LiveView.

LiveView does not use the HTTP contract or generated TypeScript: it calls the same pipelines the HTTP host does, so authorization, validation and recording behave identically on both.

defmodule MyAppWeb.AuthorsLive do
  use MyAppWeb, :live_view
  use Arc.LiveView, application: MyApp.Arc

  def mount(_params, _session, socket) do
    {:ok,
     socket
     |> assign_observable(:authors, MyApp.Authors.Listing.Authors, :live_authors)
     |> assign_form(:form, MyApp.Authors.Registration.RegisterAuthor)}
  end

  def handle_event("validate", %{"command" => params}, socket),
    do: {:noreply, validate_form(socket, :form, params)}

  def handle_event("save", %{"command" => params}, socket) do
    case submit_form(socket, :form, params) do
      {:ok, _result, socket} -> {:noreply, put_flash(socket, :info, "Registered")}
      {:error, socket} -> {:noreply, socket}
    end
  end
end

Who is the caller

The principal is read from the socket's assigns each time a command or query runs, not once at mount, so a signed-out or demoted user is caught on the next call. By default Arc reads assigns.arc_principal, then assigns.current_scope.user, then assigns.current_user. Pass principal: {Module, :function} to use Arc.LiveView to resolve it your own way; the function receives the socket and returns an Arc.Principal.

Observable queries

assign_observable/5 keeps an assign current. The subscription is a process that ends with the LiveView, and the application must be started (MyApp.Arc in your supervision tree).