Rails - 过滤多对多

Question

我在 'Event' 和 'Member' 之间有一个多对多的关系。我目前正在尝试过滤掉所有不属于某个成员的事件。

我可以做相反的事情，我可以 select 属于特定事件的所有事件。我是这样做的：

class Event < ApplicationRecord
  has_and_belongs_to_many :members
  scope :filter_by_member, -> (member) { joins(:members).where( members: { id: member.id } ) }
end

class Member < ApplicationRecord
  has_and_belongs_to_many :events
end

我试图通过将 where 更改为 where.not 来获得相反的行为（所有不属于成员的事件）；但是；这只是 select 事件 table.

中的所有记录

这是我试图在 rails 控制台中获取所有不属于成员的事件，在将 where 切换到 where.not 之后。然而，正确的输出应该是事件 2 和事件 3 在最后一行被 select 编辑（因为事件 1 属于 sample_member）；所有 3 个都在 selected.

irb(main):001:0> sample_member = Member.find(2)
  Member Load (0.3ms)  SELECT "members".* FROM "members" WHERE "members"."id" =  LIMIT   [["id", 2], ["LIMIT", 1]]
=> #<Member id: 2, uid: nil, name: "John", created_at: "2021-10-23 14:30:38.434442000 -0500", updated_at: "2021-10-23 14:30:38.434442000 -0500", isAdmin: nil, email: nil>
irb(main):002:0> sample_member.events
  Event Load (0.4ms)  SELECT "events".* FROM "events" INNER JOIN "events_members" ON "events"."id" = "events_members"."event_id" WHERE "events_members"."member_id" =   [["member_id", 2]]
=> 
[#<Event:0x00007f02f0aeb4e8
  id: 1,
  date: nil,
  description: "Please come",
  isMandatory: nil,
  location: nil,
  admin_id: nil,
  created_at: Sat, 23 Oct 2021 14:27:32.966994000 CDT -05:00,
  updated_at: Sat, 23 Oct 2021 14:27:32.966994000 CDT -05:00,
  time: nil,
  datetime: nil,
  name: "Fun event">]
irb(main):003:0> Event.filter_by_member sample_member
  Event Load (0.3ms)  SELECT "events".* FROM "events" INNER JOIN "events_members" ON "events_members"."event_id" = "events"."id" INNER JOIN "members" ON "members"."id" = "events_members"."member_id" WHERE "members"."id" !=   [["id", 2]]
=> 
[#<Event:0x00005651319bf3d8
  id: 1,
  date: nil,
  description: "Please come",
  isMandatory: nil,
  location: nil,
  admin_id: nil,
  created_at: Sat, 23 Oct 2021 14:27:32.966994000 CDT -05:00,
  updated_at: Sat, 23 Oct 2021 14:27:32.966994000 CDT -05:00,
  time: nil,
  datetime: nil,
  name: "Fun event">,
 #<Event:0x00005651319bf270
  id: 2,
  date: nil,
  description: "Important",
  isMandatory: nil,
  location: nil,
  admin_id: nil,
  created_at: Sat, 23 Oct 2021 14:29:39.380136000 CDT -05:00,
  updated_at: Sat, 23 Oct 2021 14:29:39.380136000 CDT -05:00,
  time: nil,
  datetime: nil,
  name: "Conference">,
 #<Event:0x00005651319bf158
  id: 3,
  date: nil,
  description: "this is orientation",
  isMandatory: false,
  location: "",
  admin_id: nil,
  created_at: Sat, 23 Oct 2021 14:39:13.186162000 CDT -05:00,
  updated_at: Sat, 23 Oct 2021 14:39:13.186162000 CDT -05:00,
  time: nil,
  datetime: nil,
  name: "orientation">]

有什么线索吗？

Answer 1

最简单的方法是使用 WHERE events.id NOT IN (...) 子查询：

Event.where.not(
  id: member.events
)

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