Question

I have this kind of db:schema :

articles +——-+ article_users +——+ user

How can I restrict an user to vote more than one time on an article ?

Is there a validation rule to put on model for that ?

Answer 1

Begin by replacing to a has_many :through relationship if you’re using has_and_belongs_to_many, so that you’ll be able to access the relation model, ie. : ArticleUser.

Then first validate the relation model ArticleUser :

validates_uniqueness_of :user_id, scope => :article_id

If you want to know if a user has already voted for an article, you can use something like :

ArticleUser.exists?(:user_id => @user.id, :article_id => @article.id)

or directly using the has_many relation…