foodsoft/app/helpers/deliveries_helper.rb

module DeliveriesHelper

  def link_to_invoice(delivery)
    if delivery.invoice
      link_to number_to_currency(delivery.invoice.amount), [:finance, delivery.invoice],
        :title => "Rechnung anzeigen"
    else
      link_to "Rechnung anlegen", new_finance_invoice_path(:supplier_id => delivery.supplier.id, :delivery_id => delivery.id)
    end
  end

end