Question

I am creating an application for live event merchandise sales. I have a table of inventory_events, each inventory_event represents a change in inventory over time. Because of the nature of my application I need to track 1 master inventory (all of the items in stock) and an inventory per event.

Essentially this is what my flow looks like:

• Assuming that today is an event day
• New inventory_events are created for each inventory_item being sold at the event
• these inventory_events are called ‘check ins’, they are checking the items into the event
• this creates a negative inventory_event and these items are subsequently removed from master inventory
• after an event is complete the remaining stock is ‘checked out’ of the event
• this creates a positive inventory_event and the left over items are added to inventory
• the net qty_change on these 2 transactions becomes my net items sold at this event

Currently this is how I have it set up:

• each Event has_many :inventory_events
• when creating inventory_events I am updating this via a fields_for in an Event update form
• this works fine for checking items in

My problems begin at checking items out (out of the event but into the system)

• Set up is the same as above except I need to be able to build 1 inventory_event for each check out event associated with this particular day’s event

My question is: How can I build 1 new field_for inventory event per inventory_event previously associated with this day’s event? I know I can just count the number of events & then build 1 for each but how do I do that & also maintain some information (item_id) so I am able to know that I am building a check in event for each item i had checked out on this day?

Thanks a lot.

Answer 1

You could start building a form using the previously known data. Let’s say you have

class Event
  has_many :check_ins # STI subclass of InnventoryEvent
  has_many :check_outs # same
end

Then you could prepopulate a list of checkouts, where each correspond to one of the already registered check_ins for the same event. In the end you won’t check out things that were not checked in before…

class EventCheckOutController

  def new

    @event = Event.find(params[:event_id])
    @event.check_ins.each do |ci|
      @event.check_outs.build(:item_id => ci.item_id, :amount => ci.amount)
    end

    # render....
  end
end

So the object will have all the checkouts, also preset with the same amount as initially checked out, you can change it afterwards form the form.