如何确定关联是否在ActiveRecord中更改？ [英] How to determine if association changed in ActiveRecord?

问题描述

ActiveRecord提供更改跟踪，其中调用 #name_changed？返回true / false取决于 name 属性是否更改在加载模型的时间到现在之间。

ActiveRecord offers change tracking, where calling #name_changed? returns true/false depending on whether the name attribute changed between when the model was loaded and now.

关联是否等效？我专门在寻找has_many关联，但是所有关联类型都会有用。

Is there an equivalent for associations? I am specifically looking for has_many associations, but all association types would be useful.

Rails 5.2，Ruby 2.5.1

Rails 5.2, Ruby 2.5.1

推荐答案

好，不是一个答案，但这是我想出的解决方法。

Ok, not a answer but this is a workaround I came up with.

在我的项目中我已经在使用宝石 已审核 以跟踪更改我也想接收更改的模型。在我的情况下，模型是 Location ，而我要检查位置是否已更改的模型是 Employee

In my project I was already using the gem audited to keep track of changes on the model I also want to receive changes on. In my case the model is Location and the model I want to check if the location was changes is Employee

然后在 after_save 中检查是否对该位置进行了审核，以及是否在几秒钟内创建了该审核。如果是这样，我能够检查更改。

In the after_save I then check if there is made an audit on the location and if it's created within seconds. If so, I'm able to check the changes.

简化的示例：

# app/models/location.rb
class Location < ApplicationRecord
  audited
end

# app/models/employee.rb
class Employee < ApplicationRecord
  after_save :inform_about_changes!
  belongs_to :location

  def inform_about_changes!
    last_location_change = location.audits.last
    if last_location_change.created_at.between?(2.seconds.ago, Time.now)
      if last_location_change.audited_changes.include? 'city'
        city_was = last_location_change.audited_changes[0]
      end
    end
  end
end

再一次，这不是一个答案，但是在我的情况下确实可以解决问题

Once again, this is not an answer, but it did the job in my case

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