Rails - 帮助理解如何使用 :dependent =>:破坏 [英] Rails - Help understanding how to use :dependent => :destroy

问题描述

我有以下型号:

User (id)
Project (id)
Permission (project_id, user_id)
Thread (project_id)
ThreadParticipation (thread_id, user_id)

所以这很好用，问题是这个.当用户离开或从项目中删除时，我需要删除该项目的所有 ThreadParticipation.

So that's working nicely, problem is this. When a user leaves or is removed from a project, I need all their ThreadParticipation's for that project deleted.

例如，如果用户(15)通过删除权限(user_id => 15，project_id => 3)离开项目(3)，我需要rails自动删除所有相关的ThreadParticipation记录(其中ThreadParticipation通过线程，属于 project_id 3，并且 ThreadParticipation.user_id = 15.

Example, so if user(15), leaves project(3) by deleting the permission (user_id =>15, project_id => 3), I need rails to automatically then delete all related ThreadParticipation records (where ThreadParticipation through thread, belongs to project_id 3, and ThreadParticipation.user_id = 15.

我已经试过了，但它没有做任何事情:

I've tried this, but it's not doing anything:

has_many :thread_participations, :foreign_key => :user_id, :dependent => :destroy

想法?谢谢

推荐答案

在 Permission 模型中，这样做:

In the Permission Model, do this:

before_destroy :delete_thread_participation

private
      def delete_thread_participation
         if self.threadparticipation 
           self.threadparticipation.delete_all "project_id ="+self.project_id+"and user_id="+self.user_id
         end
      end

这是考虑到您在模型中定义了关系

This is considering you have relationships defined in the models

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