在验证创建新对象时获取“ undefined method” ruby​​？

Question

I am following this post and trying to add a validate method before object creation. I keep getting undefined method 'video' for #<Video:0xbe430a0> I am reading this article here http://ruby-for-beginners.rubymonstas.org/ getting to know how ruby works but cannot figure out why I get this error.

http://api.rubyonrails.org/v5.1/classes/ActiveModel/Validations/ClassMethods.html#method-i-validate

If I call new on a ruby object and save it with a validation what do I need to do to the video variable to not get undefined method ?

class Video < ApplicationRecord

  validate :video_count_within_limit, on: :create

  def video_count_within_limit
    if video(:reload).count >= 9
      errors.add(:base, "Exceeded video limit of 9 videos")
    end
  end

Answer 1

as video method actually doesn't exists on your model, and based on post you're following it's actually a reference you should just simple replace video with self . Something like this: if self.reload.count >= 9 errors.add(:base, "Exceeded video limit of 9 videos") end Let me know if this works for you ! Regards

---

New Answer :

On post you're following, they are checking videos as association and then checking if its count bigger then 9.

How it works is actually is that the main object which is referenced to the videos is not stored to DB but it has videos association so you can check length/count of that.

In your case, if you're trying to do that on your main object ( Video ) you will get an error that it couldn't be find as it's not persisted but just instantiated as well as your validation method is called before create .

This way you're trying to achieve, it's logical only for validating creating some referenced model, which can't be stored has more then 9 videos.

Hope it's clear enough ?

Regards