eager-loading nested polymorphic associations
We have a controller action that performs n+1 queries to present associated models as nested hashes. The typical solution is to use :include to eager-load associations. Unfortunately, the models are related polymorphically, and :include can’t… Read more
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belongs_toassociations can now automatically create back references each other, thanks to a Backport of :inverse_of from Rails 3 to rails 2.3.6. This allows us to keep our object graphs more correct and avoid situations where we have 2 copies of the same object because the object graph is walked in reverse. Here's how to use it:
class Parent < ActiveRecord::Base has_one :child, :inverse_of => :parent accepts_nested_attributes_for :child end class Child < ActiveRecord::Base belongs_to :parent validates_presence_of :parent end
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Turns out that unloaded associations are not validated. Solution: load the association before calling
.valid? on the parent. In general, you should also not create invalid objects, instead using a state variable to put them into a "draft" or "incomplete" state where they are still valid but not complete. Then remove that state and you'll see the errors required to finish that object.
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