One transaction per one Object DDD

one_transaction_per_one_obj.rb

class OrdersService
  def call(command)
    case command
    when BatchOfCommands
      batch(command.commands)
    when ConfirmCommand
      confirm(command)
    when SetDeliveryMethodCommand
      set_delivery(command)
    # ...
    else
      raise ArgumentError
    end
  end

  private

  def batch(commands)
    groupped_commands = commands.group_by(&:order_number)
    groupped_commands.each do |order_number, order_commands|
      with_order(number) do
        order_commands.each{|cmd| call(cmd) }
      end
    end
  end

  def confirm(command)
    with_order(command.order_number) do |order|
      order.confirm
    end
  end

  def with_order(number)
    if @order && @order.number == number
      yield @order
    elsif @order && @order.number != number
      raise "not supported"
    else
      begin
        order_repository.transaction do
          @order = order_repository.find(number, lock: true)
          yield @order
          order_repository.save(@order)
        end
      ensure
        @order = nil
      end
    end
  end

end

batch = BatchOfCommands.new
batch.
  add_command(SetDeliveryMethodCommand.new(...)).
  add_command(ConfirmCommand.new(...))

OrdersService.new.call(batch)