Ruby-for-Beginner | scripting language designed by Yukihiro Matsumoto

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