如何通过关联在 has_many 中使用回调? [英] Howto use callbacks in a has_many through association?

问题描述

我有一个通过 has_many 关联到项目模型的任务模型，需要在通过关联删除/插入之前操作数据.

I have a Task model associated to a Project model via has_many through and need to manipulate the data before delete/insert via the association.

由于 "自动删除连接模型是直接的，不会触发销毁回调."我不能为此使用回调.

Since "Automatic deletion of join models is direct, no destroy callbacks are triggered." i can not use callbacks for this.

在任务中，我需要所有的 project_ids 来计算任务保存后的项目值.如何通过关联禁用删除或更改删除以在 has_many 上销毁?这个问题的最佳实践是什么?

In Task i need all project_ids to calculate a value for Project after Task is saved. How can i disable delete or change delete to destroy on has_many through association? What is best practise for this problem?

class Task
  has_many :project_tasks
  has_many :projects, :through => :project_tasks

class ProjectTask
  belongs_to :project
  belongs_to :task

class Project
  has_many :project_tasks
  has_many :tasks, :through => :project_tasks

推荐答案

似乎我必须使用 关联回调 before_add、after_add、before_remove 或 after_remove

Seems like i have to use associations callbacks before_add, after_add, before_remove or after_remove

class Task
  has_many :project_tasks
  has_many :projects, :through => :project_tasks, 
                      :before_remove => :my_before_remove, 
                      :after_remove => :my_after_remove
  protected

  def my_before_remove(obj)
    ...
  end

  def my_after_remove(obj)
    ...
  end
end   

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