Rails polymorphic dependent: :destroy not working correctly

Question

Let\'s say I have three Active Record models:

class Tissue
  has_many :boogers, as: :boogerable, dependent: :destroy
end

class Finger
  has_many :boogers, as: :         


        

Answer 1

First, you need to know that the ActiveRecord destroy method uses the object's :id field when it needs to destroy it. And that the dependent: :destroy option will trigger the destroy method upon all objects that are assciated with the current object.

I assume that you're doing something like this:

f = Finger.find(finger_id)
t = Tissue.find(tissue_id)

f.boogers[0].boogerable = t
f.boogers[0].save!

f.destroy

The dependent: :destroy statement means that when destroy is called upon f, it will also be called upon all boogers that are associated with f. And since f and its boogers are loaded into memory, the f.booger[0] object still exists in the array of f.boogers which will have each of its elements, including boogers[0], destroyed when f is destroyed.

The solution of this case is that you hit f.boogers.reload to update the array before calling f.destroy.

Also, please note that when you destroy f, all associated boogers will be destroyed as well, is that really what you want? destroy the finger with all remaining associated boogers when one of them is transferred to something else?