receive_purchase_order.rb

# Pseudocode for Interactor pattern
class PurchaseRecordsController
  def create 
    purchase_order = PurchaseOrder.find id
    
    # Call the organizer and pass some state
    # purchase_order can be accessed in any of the Interactors called in
    # the ReceivePurchaseOrder organizer
    result = ReceivePurchaseOrder.call(purchase_order: purchase_order)

    if result.success?
      # Access the purchase record through result.purchase_record
      puts "PurchaseRecord created successfully!"
    else
      puts "Error: #{result.message}"
    end
  end
end

class ReceivePurchaseOrder
  include Interactor::Organizer
  
  # Runs these classes in the defined order
  # if one fails, all of the previous classes will
  # run their 'rollback' functions in the reverse order.
  organize CreatePurchaseRecordInteractor,
           CreateStockLineItemInteractor,
           IdentifyNeededPartsInteractor,
           AllocateStockToPartsInteractor
end

class CreatePurchaseRecordInteractor
  include Interactor
  
  def call    
    if purchase_record = purchase_order.purchase_record.create(...)
      # Use 'context' to store state between Interactors
      context.purchase_record = purchase_record
    else
      context.fail!(message: "Failed to create Purchase Record for: #{purchase_order}")
    end
  end
  
  # rollback is called automatically if an Interactor in the chain fails
  def rollback
    context.purchase_record.delete
  end
end

class CreateStockLineItemInteractor
  include Interactor

  def call
    stock_line_item = purchase_order.stock_line_item.create(...)
    context.stock_line_item = stock_line_item
  end
  
  def rollback
    context.stock_line_item.delete
  end
end

class IdentifyNeededPartsInteractor
  include Interactor
  
  def call
    parts = Part.where('quantity_needed > 0') # obviously missing some details in this query
    context.parts = parts if parts
  end
  
  def rollback
    context.parts.delete_all
  end
end

class AllocateStockToPartsInteractor
  include Interactor

  def call
    if context.parts
      parts.each do |part|
        part_quantity = part.quantity
        part_line_item = part.part_line_items.create(...)
        
        context.part_line_items << part_line_item
        context.stock_line_item.quantity -= part_quantity
      end
    end
  end
  
  def rollback
    context.part_line_items.delete_all
  end
end