define_destroy_hook

# File activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb, line 16
      def define_destroy_hook
        name = self.name
        model.send(:include, Module.new {
          class_eval             def destroy_associations              association(#{name.to_sym.inspect}).delete_all              super            end, __FILE__, __LINE__ + 1
        })
      end