当“朋友”删除他的帐户时,如何从数据库中删除友谊?

我已经成功地实现了一个友谊模型,该模型在创建友谊时在数据库中创建两行。

 # Accept a friend request.
  def self.accept(customer, friend)
    transaction do
      accepted_at = Time.now
      accept_one_side(customer, friend, accepted_at)
      accept_one_side(friend, customer, accepted_at)
    end
  end

  # Update the db with one side of an accepted friendship request.
  def self.accept_one_side(customer, friend, accepted_at)
    request = find_by_customer_id_and_friend_id(customer, friend)
    request.status = 'accepted'
    request.accepted_at = accepted_at
    request.save!
  end

现在,当用户A删除他的帐户时,我如何确保数据库中的整个友谊(两行)也被删除。我相信 dependent: destroy 将仅在删除用户A的帐户之后删除与用户A相关的数据。但我希望数据库中属于用户B的另一行也被删除。