I was implementing dirty checking for an application, and I found something that is a little counterintuitive. Let me start with a quick quiz:
bob=User.find(1) alice=User.find(2) trip=Trip.new
trip.driver=bob old_driver=trip.driver trip.driver=alice
In this example, who is old_driver? If you guessed Alice, you're right.
Inside associations.rb, the mutator is defined as: define_method("#{reflection.name}=") do |new_value| association = instance_variable_get("@#{reflection.name}") if association.nil? association = association_proxy_class.new(self, reflection) end
association.replace(new_value)
By re-using the proxy, we get this odd assignment behavior. Is there any reason not to create a new proxy on assignment?
Simply eliminating the if condition fixes my case, and all tests still pass.
I can create a ticket with tests and a patch if I'm not missing something here.