Ruby on rails 3 是Mongoid还是Rails3的bug？下面是完整的代码，您可以复制奇怪的'；bug'；

如果您想重现问题，请跟我来：

#book.rb
class Book
  include Mongoid::Document
  include Mongoid::Timestamps

  field :name

  belongs_to :student

  validate :check

  def check
    # The calling for the 'school' method caused the issue
    self.student.school
  end

end

首先，创建这三个模型（只需复制）：

$ rails -v
Rails 3.1.1
$ ruby -v
ruby 1.9.2p312 (2011-08-11 revision 32926) [i686-linux]

---

---

其次，运行控制台并粘贴：

#book.rb
class Book
  include Mongoid::Document
  include Mongoid::Timestamps

  field :name

  belongs_to :student

  validate :check

  def check
    # The calling for the 'school' method caused the issue
    self.student.school
  end

end

---

然后，让我们看看发生了什么：

ruby-1.9.2-head :001 > School.destroy_all;Student.destroy_all; Book.destroy_all; School.create
ruby-1.9.2-head :001 >  Student.create school_id: School.first.id, 'books_attributes' => {'1' => {'name' => 'I am a book'}}

更重要的是，如果您将“学生有很多书”关系设置为“自动保存：true”：

ruby-1.9.2-head :002 > Book.count
MONGODB xxx_development['$cmd'].find({"count"=>"books", "query"=>{}, "fields"=>nil})
=> 2 

让我们看看会发生什么：

class Student
 ......
 has_many :books, autosave: true
 ......
end

ruby-1.9.2-head:001>School.all；学生，摧毁一切；毁灭一切；学校，创造
ruby-1.9.2-head:001>Student.create school\u id:school.first.id，'books\u attributes'=>{'1'=>{'name'=>'I am a book'}
ruby-1.9.2-head:002>Student.count
MONGODB xxx_开发['$cmd'].查找（{“计数”=>“学生”，“查询”=>{}，“字段”=>nil}）
=> 2 
ruby-1.9.2-head:004>Student.all.to_a
MONGODB xxx_开发['students'].查找（{}）
=> [#, #] 
ruby-1.9.2-head:005>Book.count
MONGODB xxx_开发['$cmd'].查找（{“count”=>“books”，“query”=>{}，“fields”=>nil}）
=> 2
ruby-1.9.2-head:006>Book.all.to_a
MONGODB xxx_开发['books'].查找（{}）
=> [#, #] 

这只虫子真让我抓狂。 在书籍验证方法中调用“学校”时，为什么会有其他模型

---

或者是我做错了什么？

这里的代码很好，您没有做任何不正确的事情-但是Mongoid对master或2.4.x上的相同代码没有问题。请参见我的建议，以找到罪魁祸首：

---

谢谢Durran，当我创建一个新的空rails应用程序来测试它时，问题仍然存在；但是在从github将我的mongoid（2.3.x）更新到最新版本后，现在一切正常了。：）

class Student
 ......
 has_many :books, autosave: true
 ......
end

ruby-1.9.2-head :001 > School.destroy_all;Student.destroy_all; Book.destroy_all; School.create
ruby-1.9.2-head :001 >  Student.create school_id: School.first.id, 'books_attributes' => {'1' => {'name' => 'I am a book'}}
ruby-1.9.2-head :002 > Student.count
MONGODB xxx_development['$cmd'].find({"count"=>"students", "query"=>{}, "fields"=>nil})
 => 2 

ruby-1.9.2-head :004 > Student.all.to_a
MONGODB xxx_development['students'].find({})
 => [#<Student _id: 4f62a8341d41c81bc6000002, _type: nil, created_at: 2012-03-16 02:40:52 UTC, updated_at: 2012-03-16 02:40:52 UTC, school_id: BSON::ObjectId('4f62a8341d41c81bc6000001')>, #<Student _id: 4f62a8341d41c81bc6000003, _type: nil, created_at: 2012-03-16 02:40:52 UTC, updated_at: 2012-03-16 02:40:52 UTC, school_id: nil>] 

ruby-1.9.2-head :005 > Book.count
MONGODB xxx_development['$cmd'].find({"count"=>"books", "query"=>{}, "fields"=>nil})
 => 2
ruby-1.9.2-head :006 > Book.all.to_a
MONGODB xxx_development['books'].find({})
 => [#<Book _id: 4f62a8341d41c81bc6000003, _type: nil, created_at: 2012-03-16 02:40:52 UTC, updated_at: 2012-03-16 02:40:52 UTC, name: "I am a book", student_id: BSON::ObjectId('4f62a8341d41c81bc6000002')>, #<Book _id: 4f62a8341d41c81bc6000002, _type: nil, created_at: 2012-03-16 02:40:52 UTC, updated_at: 2012-03-16 02:40:52 UTC, name: nil, student_id: nil>]