ID和Type相同不创建多态关联？

Question

I'm having trouble getting my validation to act correctly.

I keep getting the error because of my validate method:

NoMethodError in ProductsController#subscribe_product

undefined method `subscriptions' for #<Class:0x6da5890>

---

class Subscription < ActiveRecord::Base
  belongs_to :subscriber, :class_name => "User"
  belongs_to :subscribable, :polymorphic => true

  validates :subscriber_id, :presence => true
  validates :subscribable_id, :presence => true
  validates :subscribable_type, :presence => true

  validate do |s|
    if s.subscribable_type.constantize.subscriptions.find_by_subscribable_id_and_subscribable_type(s.subscribable_id, s.subscribable_type)
      s.errors.add_to_base "You're already susbcribed to this Product."
    end
  end
end

---

Then I have a link you can click to subscribe to a product in the controller:

def subscribe_product
 @product = Product.find(params[:id])
 subscription = Subscription.new
 subscription.subscriber = current_user
 @product.subscriptions << subscription
 @product.save
 redirect_to :back
end

Why am I getting this error?

Answer 1

Add to subscription model:

validates_uniqueness_of :subscribable_id, :scope => [:subscriber_id, subscribable_type]

And make sure you have has_many:subscriptions defined in product.rb