ruby-on-rails - 如果 ID 和 Type 相同，不创建多态关联？

Question

我无法让我的验证正确执行。

由于我的validate方法，我不断收到错误：

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

---

然后我有一个链接，您可以单击以订阅控制器中的产品：

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

为什么我会收到此错误？

Answer 1

添加到订阅模型：

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

并确保您在 product.rb 中定义了 has_many :subscriptions