before_save中的mark_for_destruction

Question

这个before_save-callback有什么问题？

class Order < ActiveRecord::Base

    has_many :line_items, :dependent => :destroy, :inverse_of => :order
    accepts_nested_attributes_for :line_items  
    attr_accessible :line_items_attributes


    before_save :mark_line_items_for_removal

    def mark_line_items_for_removal
      line_items.each do |line_item|
         line_item.mark_for_destruction if line_item.quantity.to_f <= 0
      end
    end
end

当其中一个line_items被标记为销毁时，将不会保存任何line_item。但是，父Order对象确实会被保存。返回true无关紧要...

关于mark_for_destruction：http://apidock.com/rails/v3.1.0/ActiveRecord/AutosaveAssociation/mark_for_destruction，为什么不是":allow_destroy => true"？查看此处：http://weblogs.manas.com.ar/spalladino/2010/03/15/deleting-children-with-accepts_nested_attributes_for-in-rails/

Answer 1

我认为您需要为has_many定义设置:autosave => true选项。

如上所述，这里：

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_many

如果为true，则在保存父对象时，始终保存关联的对象或销毁标记为销毁的对象。如果为false，则从不保存或销毁关联的对象。默认情况下，仅保存作为新记录的关联对象。