Model Serialization in Session
2005-10-21
I needed to save my products in the session for the cart. My product has a belongs_to relationship with a picture object, which has the full data in the DB (20+ Kb/picture).
Obviously, saving the whole products database in the session would be unfeasible. So, I dug into the Ruby Marshal class documentation, and came up with the following solution:
1 class Product < ActiveRecord::Base 2 def _dump(ignored) 3 self.id.to_s 4 end 5 6 def self._load(id) 7 find(id) 8 end 9 end
Instead of saving the whole object, what I’m saving is only the model’s ID. On reload, I simply fetch the object from the DB again. That way, my sessions stay nice and small, but I have the full object at my disposal when I want to work with the object.
One last thing. I coded a test which makes sure that things will always stay nice and small:
1 class ProductTest < Test::Unit::TestCase 2 def test_dumping_loading 3 prod = Product.find(:first) 4 stream = Marshal.dump(prod) 5 assert stream.length < 32, 6 "Dumped stream exceeds 20 bytes treshold: #{stream.size}" 7 assert_equal prod, Marshal.load(stream) 8 end 9 end
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