es_slides.rb

class WeeklyAppointmentsProjector
  include Projector
  processes_events :appointment_scheduled,
                   :appointment_rescheduled,
                   :appointment_name_changed,
                   :appointment_canceled

  table :weekly_appointments do
    # ...
  end

  def project(event)
  end
end






if event.type == :appointment_scheduled
  table.insert(
    year: event.body.start_time.year,
    week_of_year: event.body.start_time.cweek,
    appointment_id: event.aggregate_id,
    appointment_name: event.body.name,
    appointment_start_time: event.body.start_time,
    appointment_end_time: event.body.end_time,
  )
end





if event.type == :appointment_rescheduled
  table
    .where(appointment_id: event.aggregate_id)
    .update(
      year: event.body.start_time.year,
      week_of_year: event.body.start_time.cweek,
      appointment_start_time: event.body.start_time,
      appointment_end_time: event.body.end_time,
    )
end



if event.type == :appointment_canceled
  table
    .where(appointment_id: event.aggregate_id)
    .delete
end



table.where(year: 2016, week_of_year: 13)





class AppointmentDetailProjector
  include Projector
  processes_events :appointment_scheduled,
                   :appointment_rescheduled,
                   :appointment_name_changed,
                   :appointment_location_moved,
                   :appointment_canceled

  table :appointment_detail do
    # ...
  end

  def project(event)
  end
end





class InvitationSender
  include DownstreamEventProcessor
  processes_events :participant_invited

  def process(event)
    InvitationEmailer.deliver!(
      email: event.body.participant_email
      appointment_details: event.body.appointment_details
    )

    emit_event Event.new(
      type: :invitation_sent,
      aggregate_id: event.aggregate_id
    )
  end
end



def process_order
  ActiveRecord::Base.transaction do
    charge_credit_card
    do_fraud_checks
    save_order
    generate_invoice
    send_invoice
    generate_shipping_label
    send_shipping_label_to_warehouse
    and_all_the_other_things
  end
end



def process_order
  ActiveRecord::Base.transaction do
    charge_credit_card
    do_fraud_checks
    order = save_order

    InvoiceGenerator.perform_async(order.id)
    InvoiceSender.perform_async(order.id)
    ShippingLabelGenerator.perform_async(order.id)
    ShippingLabelDeliverer.perform_async(order.id)
  end
end