What's the best way to destroy both sides of a self-referential association?

In my project, I have a self-referential association.

I have a User model:

class User < ActiveRecord::Base
  has_many :relationships, :dependent => :destroy
  has_many :peers, :through => :relationships
end

And a Relationship model:

class Relationship < ActiveRecord::Base
  belongs_to :user
  belongs_to :peer, :class_name => "User"
end

When two users are peers with one another, there are obviously two records in the database.

When one user opts to end a relationship, I'd like this to destroy both records - not just one side of the relationship.

Is there a better way to go about doing this rather than loading the relationship twice in the controller (once for each side开发者_StackOverflow of the relationship)?

Couple of ways this can be done

Firstly is an after delete trigger, this is a pretty controversial way of doing things if you believe in the false promise of database agnosticism, however is one that works - in essence, you look at old.peer_id and old.user_id and then do a delete but reversing the roles. If you want to go down this route, you should consult your database manual as how to implement a trigger.

The second way is an after_destroy callback where you do a

after_destroy do |record| 
  other = Relationship.find_by_user_id_and_peer_id(record.peer_id, record.user_id)
  other.destroy if other
end

The other - and probably more drastic measure is to rework the model, so that it has a boolean accepted field wherein both sides of the relationship are modelled by one record in the database, there is a constraint on records where (peer_id, user_id) = (user_id, peer_id). That way you wont have to worry about deleting both sides, nor having duplicate records.