How to validate unique id's in two columns in rails?

问题

I know that to prevent this from happening:

user_id: 10 | friend_id: 20

user_id: 10 | friend_id: 20

You can use

validates :user_id, uniqueness: {scope: :friend_id}

But what if you want to prevent a user from adding himself as a his own friend?

user_id: 10 | friend_id: 10

回答1:

This should work. You're ensuring that friend_id can't equal user_id

validates :friend_id, exclusion: {in: ->(u) { [u.user_id] }}

来源：https://stackoverflow.com/questions/33698881/how-to-validate-unique-ids-in-two-columns-in-rails