I have two models, one Post and Genre. I'm creating new post with given genre_id. What is the best way of validating if genre with given id exists? For now I'm validating presence of genre_id, but it's not enough.
validates :genre_id, presence: true
I know I can check whether the genre exists in a controller, but I would prefer to have this in my post validator object.
You can explicitly tell Rails to validate the genre association and not just the attribute, genre_id with:
has_one :genre
validates_presence_of :genre