我在“事件”和“成員”之間存在多對多關系。我目前正在嘗試過濾掉不屬于某個成員的所有事件。
我可以做相反的事情，我可以選擇屬于特定事件的所有事件。我是這樣做的：
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
但是，我試圖通過更改where為來獲得反向行為（所有不屬于成員的事件）where.not；這只是選擇事件表中的所有記錄。
這是我嘗試在切換where到where.not. 然而，正確的輸出應該是在最后一行中選擇了事件 2 和 3（因為事件 1 屬于 sample_member）；3個都被選中了。
irb(main):001:0> sample_member = Member.find(2)
Member Load (0.3ms) SELECT "members".* FROM "members" WHERE "members"."id" = $1 LIMIT $2 [["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" = $1 [["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" != $1 [["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">]
有什么線索嗎？
uj5u.com熱心網友回復：
最簡單的方法是使用WHERE events.id NOT IN (...)子查詢：
Event.where.not(
id: member.events
)
轉載請註明出處，本文鏈接：https://www.uj5u.com/ruanti/338833.html
標籤：红宝石轨道 PostgreSQL 活动记录 多对多 关系型数据库
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