Rails 3和ActiveAdmin：获取表单上关联记录的值

Question

Ok, I think this is going to be tricky on ActiveAdmin.

I need to issue a pop-up warning (I'll probably use jQuery) if there is an invoice created for a certain customer. This would be easy if the invoice form had a select menu for the customers, but that's not my setup. Instead, this is the way it works:

Shipment has_one Invoice
Shipment belongs_to Customer
(the New Shipment form has a select menu for customer)

Invoice belongs_to Shipment

So in my New Invoice form, I have a select menu for shipments. To find out what customer the invoices belongs to, if i contains an instance of invoice I do i.shipment.customer .

# this is a snippet of my New Invoice form
form do |f|
f.inputs "Shipment Details" do      
  f.input :shipment_id, :label => "Shipment", :as => :select, :collection => Shipment.find(:all, :order => "file_number", :select => "id, file_number").map{|v| [v.file_number, v.id] }
  f.input :issued_at, :label => "Date", :as => :datepicker
  f.input :accounting_month, :label => "Accounting month", :as => :datepicker
end

In the New Invoice form: how can I get the customer the shipment belongs to from the shipments select menu.

For example, user selects Shipment #1231. If shipment belongs to customer_id 5, display jQuery alert.

(I already know how to include a javascript file in ActiveAdmin: Active Admin: Including Javascript )

Answer 1

What you can do: make the collection for the shipment select list display the customer the 'current' invoice is connected to. So for the collection you could join with the Customer model, like so:

f.input :shipment_id, :label => "Shipment", :as => :select, 
        :collection => 
          Shipment.
              joins(:customer).
              order('shipments.file_number').
              select("shipments.id, shipments.file_number || ' ' ||  customers.your_beautiful_customer_attribute as concatted").
              map{|v| [v.concatted, v.id] }

Hope it helps.