How do I keep two records, for different models, in sync without falling into the callback trap?

Question

I have attributes on two models that I would like to keep in sync.

1.9.3p194 :009 > p
 => #<Product id: 19, name: "Long Sleeve Blue", description: "<p>\tLong Sleeve Blue Flannel shirt comes in all siz...", price: 49.99, vendor_id: 12, created_at: "2012-12-15 23:35:05", updated_at: "2013-01-24 19:11:18", image: "shirt.png", sku: "ABC10034"> 
1.9.3p194 :010 > p.piggybak_sellable
 => #<Piggybak::Sellable id: 1, sku: "AR4590", description: "Blue Shirt", price: #<BigDecimal:7fa97cd63ff8,'0.2499E2',18(45)>, quantity: 100, item_id: 19, item_type: "Product", active: true, unlimited_inventory: false>

Both of those share some attributes that are similar.

I have the creation aspect down - once a new record is created, I simply do an after_create.

The issue is with the updating of the record.

If I call an after_save and do an update_attributes in the method called by the after_save it starts an infinite loop and crashes the app.

How do I achieve that - given that I want to update many columns?

I know one solution is to use update_column - but that just works with 1 column.

Thoughts?

I assume if they are sync'ed..... they have some type of association? Why not just reference the other model's attributes? — omarvelous, Jan 25 '13 at 20:55
Because I am using a gem - piggybak - that sets up the association, but it's not as simple as a regular AR assocation, because the gem is actually a Rails Engine. I explored some stuff related to that here - http://stackoverflow.com/questions/14517088/how-do-i-update-the-attributes-of-an-attribute-on-an-ar-model/14527839#14527839 — marcamillion, Jan 25 '13 at 21:44

score 1 · Answer 1 · edited May 23 '17 at 10:34

You could temporarily deactivate the callback on the other model in each of your after_save callbacks to avoid looping like this. For the details on doing this, see the second answer of this question How to skip ActiveRecord callbacks?

Would probably look something like this:

after_save :update_product

def update_product
  Product.skip_callback(:save, :after, :update_other)
  p = Product.find_by_whatever(self.whatever)
  p.update_attributes(:one => self.one, :two => self.two)
  Product.set_callback(:save, :after, :update_other)
end

How do I keep two records, for different models, in sync without falling into the callback trap?

1 Answers1