为什么我的after_save回调会阻止我的ActiveRecord关联正确保存？

Question

当我注释掉我的after_save回调时，我的ActiveRecord关联工作得很好。在Rails控制台，你会看到：

> @report = Report.create :name => "foo" 
=> #<Report id: 9, name: "foo", created_at: "2013-03-05 09:51:55", updated_at: "2013-03-05 09:51:55"> 
> @question = @report.questions.create :description => "bar" 
=> #<Question id: 18, standard_id: nil, description: "bar", element_id: nil, condition_id: nil, blueprint_name: nil, blueprint_url: nil, created_at: "2013-03-05 09:52:32", updated_at: "2013-03-05 09:52:32", additive: false, instructions: nil> 
> @report.questions 
=> [#<Question id: 18, standard_id: nil, description: "bar", element_id: nil, condition_id: nil, blueprint_name: nil, blueprint_url: nil, created_at: "2013-03-05 09:52:32", updated_at: "2013-03-05 09:52:32", additive: false, instructions: nil>] 
> @question.reports 
=> [#<Report id: 9, name: "foo", created_at: "2013-03-05 09:51:55", updated_at: "2013-03-05 09:51:55">] 

然而，协会停止工作，当我添加after_save回调question.rb如下：

def create_matching_surveys 
    self.reports.each do |report| 
     report.reviews.each do |review| 
     review.competitors.each do |competitor| 
      competitor.surveys.find_or_create_by_question_id(self.id) 
     end 
     end 
    end 
    end 

然后，在Rails的控制台，您可以：

> @report = Report.create :name => "foo" 
=> #<Report id: 13, name: "foo", created_at: "2013-03-05 10:20:51", updated_at: "2013-03-05 10:20:51"> 
> @question = @report.questions.create :description => "bar" 
=> #<Question id: 24, standard_id: nil, description: "bar", element_id: nil, condition_id: nil, blueprint_name: nil, blueprint_url: nil, created_at: "2013-03-05 10:21:02", updated_at: "2013-03-05 10:21:02", additive: false, instructions: nil> 
> @report.questions 
=> [#<Question id: 24, standard_id: nil, description: "bar", element_id: nil, condition_id: nil, blueprint_name: nil, blueprint_url: nil, created_at: "2013-03-05 10:21:02", updated_at: "2013-03-05 10:21:02", additive: false, instructions: nil>] 
> @question.reports 
=> [] 

无论报告是否包含具有竞争对手的评论，都会发生这种情况。

奇怪的是我认为回调是在问题被保存后发生的？因此，在这种情况发生之前，协会应该保存这些权利，对吗？

我该如何解决？

UPDATE

我想我有打电话给在对象的生命周期中的正确位置的回调，但我不能找到那个地方。这就是为什么我认为这一点：

> @report = Report.create :name => "foo" 
=> #<Report id: 20, name: "foo", created_at: "2013-03-05 12:29:35", updated_at: "2013-03-05 12:29:35"> 
> @question = @report.questions.create :description => "bar" 
=> #<Question id: 31, standard_id: nil, description: "bar", element_id: nil, condition_id: nil, blueprint_name: nil, blueprint_url: nil, created_at: "2013-03-05 12:30:14", updated_at: "2013-03-05 12:30:14", additive: false, instructions: nil> 
> @question.reports 
=> [] 
> @question.update_attributes :description => "foo" 
=> true 
> @question.reports 
=> [#<Report id: 20, name: "foo", created_at: "2013-03-05 12:29:35", updated_at: "2013-03-05 12:29:35">] 

顺便说一句，现在的这个方法是在question_observer.rb：

class QuestionObserver < ActiveRecord::Observer 

    def after_save(model) 
    model.reload 
    model.reports.reload 
    model.reports.each do |report| 
     report.reviews.each do |review| 
     review.competitors.each do |competitor| 
      competitor.surveys.find_or_create_by_question_id(model.id) 
     end 
     end 
    end 
    return true 
    end 

end 

Answer 1

答案是使用名为after_commit一个整洁的新的回调挂钩，将其用Rails 3的推出。

参见http://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html#method-i-after_commit。

唯一的问题是after_commit不工作“开箱即用”事务性灯具，但也有很多解决方案，在那里，我发现这个工作很适合我：https://supportbee.com/devblog/2012/01/14/testing-after_commitafter_transaction-with-rspec/