活动记录关联上的回调

class Entry < ActiveRecord::Base
  def after_destroy
    Entry.where(:vacation_id => self.vacation_id).each {|entry| entry.destroy}
  end
end

class EntriesController < ApplicationController
  def destroy
    @entry = Entry.find(params[:id])
    @entries = Entry.where(:vacation_id => @entry.vacation_id).each {|entry| entry.destroy}
    #send email here
    ...
  end
end

before_destroy

class VacationRequest < ActiveRecord::Base
  has_many :entries
end

class Entry < ActiveRecord::Base
  belongs_to :vacation_request
  before_destroy :destroy_others
  def destroy_others
    self.vacation_request.entries.each do |e|
      e.mark_for_destruction unless e.marked_for_destruction?
    end
  end
end

class Entry < ActiveRecord::Base
  belongs_to :vacation_request, :dependent => :destroy

  # ...
end

class VacationApproval < ActiveRecord::Base
  has_many :entries, :dependent => :destroy

  # ...
end

class VacationApproval < ActiveRecord::Base
  has_many :entries , :conditions => {:job_id => Job.VACATION.id }, :dependent => :nullify

class Entry < ActiveRecord::Base
  validates_presence_of :vacation_approval_id ,:if => lambda {|entry| entry.job_id == Job.VACATION.id} , :message => \"This Vacation Has Been Canceled. Please Delete These Entries.\"

@entries.each {|entry| entry.destroy if entry.invalid? }

`raise \"Entries are not valid, please check them and try again ( Did you cancel your vacation? )\" if @entries.any? &:invalid?` 

class VacationApproval < ActiveRecord::Base
    has_many :entries , :conditions => {:job_id => Job.VACATION.id }, :dependent => :delete_all
end

class Entry < ActiveRecord::Base  
  after_destroy :cancel_vacation_on_destory
  def cancel_vacation_on_destory
    if !self.vacation_approval.nil?
      self.vacation_approval.destroy
    end
  end
end