Validate scoped uniqueness in polymorphic association models

Question

Right, so I have a polymorphic association that allows for different object types to be favorited. So a person can favorite a product, or a person, or whatever. What I want to d

Answer 1

If you closely observe you can find that uniqueness validation just work fine :)

validates :user_id, :uniqueness => { :scope => [:favoritable_type, :favoritable_id] }

Look at the data image you added. inside image you can find out that second record is not having favouritable whereas first have which is different hence 2 records are uniq and its not issue with uniqueness but its your logical gap.

If you strictly wanted to avoid second entry then keep favouritable as mandatory field

validates :favoritable_type, :favoritable_id, :presence => true

Answer 2

class Favorite < ActiveRecord::Base

  belongs_to :user
  belongs_to :favoritable, polymorphic: true

  validates :user_id, :favoritable_id, presence: true,
    numericality: { only_integer: true }

  validates :favoritable_type, presence: true,
    inclusion: { 
      in: %w(FirstModelName SecondModelName),
      message: "%{value} is not a valid" 
    }

  validates :user_id, uniqueness: { scope: [ :favoritable_type, :favoritable_id ] }
end