如何破坏..与has_many

Question

有模型：member(id，project_id，user_id(，project(id(，user(id(，somemodel(id，project_id，user_id(。

• 成员belongs_to :p roject， belongs_to ：用户

• somemodel belongs_to :p roject， belongs_to ：user

我希望在删除成员时删除某个

模型，以便也删除某个模型(与该成员project_id和user_id相同(。怎么做？

为此，我希望将has_many :somemodels, dependent: :destroy添加到成员中，但我不知道在成员类中给has_many :somemodels正确的参数。 has_many :somemodels, dependent: :destroy单独不起作用，因为它尝试通过 somemodels 表中不存在的member_id搜索某个模型，因此会发生no column错误。

添加到会员的合适has_many :somemodels ...是什么？

Answer 1

另一种方法是为此特定关系创建一个:through关联，然后将该关联设置为 dependent: :destroy 。我认为它的结构是这样的：

class Member < ActiveRecord::Base
  belongs_to :user
  belongs_to :project
  has_many :some_models, ->(member) { where(user_id: member.user_id) },
                         through: :project,
                         dependent: :destroy
end

我

还没有测试过它，但据我所知，它似乎是正确的。

Answer 2

我认为您应该为Member模型添加一个after_destroy回调：

# In member model
class Member < ApplicationRecord
    after_destroy :also_destroy_somemodel
    ...
   def also_destroy_somemodel
       # Fast, use in case somemodel dont have any callbacks
       Somemodel.where(project_id: project_id, user_id: user_id).delete_all
       # Or
       # Slow, use in case somemodel has callback(s)
       # Somemodel.where(project_id: project_id, user_id: user_id).each &:destroy
   end
end

希望对您有所帮助。