Hi,
On AWDWR page 332 there is this example
class Order < ActiveRecord::Base has_one :invoice end
order = Order.new(... attributes ...) invoice = Invoice.new(... attributes ...) order.invoice = invoice
And then the explanation: If there is already an existing child object when you assign a new object to a has_one association, that existing object will be updated to remove its foreign key association with the parent row(the foreign key will be set to null)
I find that however that if:
1) I change has_one :invoice :dependent => :destroy then the existing object is actually DELETED rather than just FK being set to null
2) However for the same has_one :invoice :dependent => :destroy if I use build_invoice instead of assignment i.e. order.build_invoice instead of order.invoice = invoice then the Existing object's FK is NULLED out and NOT deleted.
I'm just trying to figure if:
a) Both observations above are correct b) Why the difference in behavior - i.e. assignment DELETEs the existing record, whereas build_association NULLs the FK
