Appending events from a controller

To record an event, build it and call .append on the stream for the relevant entity. The result behaves exactly like saving an ActiveRecord model:

# app/controllers/debts_controller.rb
class DebtsController < ApplicationController
  def new
    @event = Debt::Issued.new
  end

  def create
    @event = Debt::Issued.new(event_params)
    debt_stream = DebtEventStream.for(debt_id)
    debt_stream.append(@event)

    if @event.persisted?
      redirect_to debt_path(debt_stream)
    else
      render :new, status: :unprocessable_entity
    end
  end

  private
      def event_params
        params.require(:debt_issued).permit(:amount, :interest_rate, :at)
      end

      def debt_id
        # Your logic to define the stream id - it can use UUID, ULID, nanoid, etc
      end
end

Four lines in this controller are pure Rails idiom — nothing about events forces you to learn a new pattern:

• Debt::Issued.new in new — the same shape as User.new or Order.new in any controller. The event class IS the model you hand to the form; there’s no Funes:: factory in the way.
• params.require(:debt_issued).permit(:amount, :interest_rate, :at) — strong parameters work as-is. The event class name is the param key, and the permitted attributes are the same ones you declared on the event class. Funes plugs straight into ActionController::StrongParameters.
• if @event.persisted? — the same outcome check you’d write as if @user.save after a standard save call. The branch shape (if @event.persisted? ... else render :new ... end) is the one you’ve written for ActiveRecord forms a hundred times.
• redirect_to debt_path(event_stream) — event streams plug into Rails URL helpers just like an ActiveRecord model. Pass one to redirect_to, link_to, or any <resource>_path helper and Rails resolves the identifier on its own, with no extra wiring.