在删除最后一个“有多个:通过”记录后销毁关联

after_destroy 回调,例如:

class Parent < ActiveRecord::Base
  has_many :children, :through => :parentage
  after_destroy :destroy_orphaned_children

  private

  def destroy_orphaned_children
    children.each do |child|
      child.destroy if child.parents.empty?
    end
  end

end

在连接模型上,使用“属于:模型,依赖::销毁”

例如,如果你想在一个病人的医生被毁灭后毁灭他,而医生已经安排了很多病人

Class Appointment
  belongs_to :doctor
  belongs_to :patient, dependent: :destroy

Class Doctor
  has_many :appointments, dependent: :destroy
  has_many :patients, through: :appointments

Class Patient
  has_many :appointments
  has_many :doctors, through: :appointments