Rails 在更新中对 Accepts_nested_attributes_for 和 habtm 关联进行验证会重置关联

Question

在 Rails 2.3.8 中，如果我在验证中循环或什至检查 habtm 关联，则我在对 Accepts_nested_attributes_for 关联进行验证时遇到问题，课程将被加载，并且任何更新都会丢失。例如，我有以下架构：

ActiveRecord::Schema.define(:version => 20100829151836) do

 create_table "attendees", :force => true do |t|
  t.integer  "lesson_set_id"
  t.string   "name"
  t.datetime "created_at"
  t.datetime "updated_at"
 end

 create_table "lesson_sets", :force => true do |t|
  t.datetime "created_at"
  t.datetime "updated_at"
 end 

 create_table "lesson_sets_lessons", :id => false, :force => true do |t|
  t.integer "lesson_id"
  t.integer "lesson_set_id"
 end

 create_table "lessons", :force => true do |t|
  t.integer  "activity_id"
  t.integer  "limit"
  t.datetime "created_at"
  t.datetime "updated_at"
 end
end

和以下模型：

class Attendee < ActiveRecord::Base
 belongs_to :lesson_sets
end
class Lesson < ActiveRecord::Base
 has_and_belongs_to_many :lesson_sets
end
class LessonSet < ActiveRecord::Base
 has_and_belongs_to_many :lessons
 has_many :attendees
 accepts_nested_attributes_for :lessons
 validate do |lesson_set|
  lesson_set.lessons.each do |l| 
   if l.limit < attendees.count
    self.errors.add_to_base("Sorry only #{l.limit} people allowed on lesson")
   end
  end
 end
end

如果我调用以下内容：

>> ls = LessonSet.first
=> #<LessonSet id: 1, created_at: "2010-08-29 07:50:23", updated_
at: "2010-08-29 07:50:23">
>> Lesson.last
=> #<Lesson id: 1, activity_id: 29, created_at: "2010-08-29 07:57:13", updated_a
t: "2010-08-29 17:04:34", limit: 5>
params = {"lessons_attributes"=>{"0"=>{"activity_id"=>"3", "id"=>"1", "_destroy"=>""}}, "id"=>"1"}
=> {"id"=>"1", "lessons_attributes"=>{"0"=>{"activity_id"=>"3", "id"=>"1", "_des
troy"=>""}}}
>> ls.update_attributes(params)
=> true
>> Lesson.last
=> #<Lesson id: 1, activity_id: 29, created_at: "2010-08-29 07:57:13", updated_a
t: "2010-08-29 17:04:34", limit: 5>
>> params = {"lessons_attributes"=>{"0"=>{"activity_id"=>"29", "id"=>"1", "_de>
=> {"id"=>"1", "lessons_attributes"=>{"0"=>{"activity_id"=>"29", "id"=>"1", "_de
stroy"=>""}}}
>> ls.update_attributes(params)
=> true
<y_id"=>"3", "id"=>"1", "_destroy"=>""}}, "id"=>"1"}
=> {"id"=>"1", "lessons_attributes"=>{"0"=>{"activity_id"=>"3", "id"=>"1", "_des
troy"=>""}}}
>> Lesson.last
=> #<Lesson id: 1, activity_id: 29, created_at: "2010-08-29 07:57:13", updated_a
t: "2010-08-29 17:04:34", limit: 5>
>> ls.update_attributes(params)
=> true
>> Lesson.last
=> #<Lesson id: 1, activity_id: 3, created_at: "2010-08-29 07:57:13", updated_at
: "2010-08-29 17:13:36", limit: 5>

这基本上是：
最后一课以 Activity_id 29 开始
在 Lesson_set 上调用 update_attributes 来尝试将 Activity_id 设置为 3
它返回 true，但是当我们看上一课时它并没有改变
然后将活动ID设置为29，即。相同并调用 update_attributes
Activity_id 仍然是 29
但随后再次致电尝试将其设置为 3
这次更新了课程。？？？

我的代码有问题吗，这对我来说似乎很奇怪，而且我在网上找不到任何类似的东西。

我想我即将迎来被打头的时刻了！

Answer 1

与以上型号
课程 has_and_belongs_to_many Lesson_sets
参加者属于Lesson_set

尝试验证参加者人数不应超过限制，这意味着在保存新关联之前，课程和Lesson_sets之间的关联在验证过程中被重置。

将验证逻辑从lesson_set移动到Attendee使验证能够工作。

因此，如果您遇到类似的情况，请尝试将验证逻辑从加入模型移动到它加入的模型之一