Question

用户U1与用户U2共享笔记N1，用户U2与用户U3共享笔记。当用户U1从笔记N1中删除用户U2时，用户U3也应该也看不到笔记。如何实现这个？什么是我的模型看起来像先感谢您这就是我的表格的样子： -

ActiveRecord::Schema.define(version: 20170909050804) do

  create_table "note_permissions", force: :cascade do |t|
    t.integer "note_id",       null: false
    t.integer "student_id",    null: false
    t.integer "granted_by_id"
    t.index ["granted_by_id"], name: "index_note_permissions_on_granted_by_id"
    t.index ["note_id", "student_id", "granted_by_id"], name: "my_index", unique: true
    t.index ["note_id"], name: "index_note_permissions_on_note_id"
    t.index ["student_id"], name: "index_note_permissions_on_student_id"
  end

  create_table "notes", force: :cascade do |t|
    t.string   "body"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "students", force: :cascade do |t|
    t.string   "name"
    t.integer  "rollnumber"
    t.string   "subject"
    t.string   "room_no"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end    
end

这是我的模特

class Note < ApplicationRecord
    has_many :note_permissions  
end

class NotePermission < ApplicationRecord
  belongs_to :note
  belongs_to :student
  belongs_to :granted_by, class_name: "NotePermission", dependent: :destroy
end

class Student < ApplicationRecord
  has_many :note_permissions
  has_many :notes, through: :note_permissions
end

Answer 1

所以你有一个权限树，从U1授予他们（U2）权限的访问权限U1开始，U2授予U3反过来。

这可以通过对注释具有单个root权限（对于U1），然后使用外键通过另一个权限授予所有其他权限

类似的东西：

create_table :notes do |t|
  # fields
end
create_table :note_permissions do |t|
  t.belongs_to :note,       null: false, foreign_key: true, on_delete: :cascade
  t.belongs_to :user,       null: false, foreign_key: true, on_delete: :cascade
  t.belongs_to :granted_by, null: true
  t.foreign_key :note_permissions, column: :granted_by_id, on_delete: :cascade
  t.index [:note_id, :user_id, :granted_by_id], unique: true
end

class Note < ApplicationRecord
  has_many :note_permissions
end
class NotePermission < ApplicationRecord
  belongs_to :note
  belongs_to :user
  belongs_to :granted_by, class_name: "NotePermission", dependent: :destroy
end
class User < ApplicationRecord
  has_many :note_permissions
  has_many :notes, through: :note_permissions
end

现在，当用户创建记事时，也会创建匹配的NotePermission（granted_by: nil，因此根目录。）

# Plus other fields you want, like its contents
# Create a note with user_1
note = Note.create(note_permissions: [NotePermission.new(user: user_1)])

会做类似的事情：

BEGIN
  INSERT INTO "notes" DEFAULT VALUES RETURNING "id"
  INSERT INTO "note_permissions" ("note_id", "user_id") VALUES ($1, $2) RETURNING "id"  [["note_id", 2], ["user_id", 1]]
COMMIT

任何NotePermission条记录与其用户ID匹配的用户都有权访问权限，当他们授予其他人权限时，请将NotePermission记录用作granted_by。

user_1.notes.find 1 # note
user_2.notes.find 1 # ActiveRecordNotFound

# user_1 grants user_2 permission
NotePermission.create!(note: note, user: user_2, granted_by: user_1.note_permissions.find_by(note: note))
# user_2 can now see
user_2.notes.find 1 # note
# user_2 grants user_3 permission
NotePermission.create!(note: note, user: user_3, granted_by: user_2.note_permissions.find_by(note: note))

您可能希望禁止两次授予用户权限（更改唯一约束），例如U1 -> U2 -> U4和U1 -> U3 -> U4），或者您需要在U4授予U5时处理多条路径（因为您现在有U1 -> U2 -> U4 -> U5 AND U1 -> U3 -> U4 -> U5）

当您删除NotePermission时，您将通过granted_by对他们授予的任何内容失效。

# Now have 3 permissions
NotePermission.all
NotePermission id: 1, note_id: 1, user_id: 1, granted_by_id: nil
NotePermission id: 2, note_id: 1, user_id: 2, granted_by_id: 1
NotePermission id: 3, note_id: 1, user_id: 3, granted_by_id: 2

# user_1 removes user_2
NotePermission.where(note: note, user_id: 2, granted_by: user_1.note_permissions.find_by(note: note)).delete_all
# Executes `DELETE FROM "note_permissions" WHERE "note_permissions"."note_id" = 1 AND "note_permissions"."user_id" = 1 AND "note_permissions"."granted_by_id" = 1`
# Because of the cascade, now have
NotePermission.all
NotePermission id: 1, note_id: 1, user_id: 1, granted_by_id: nil

# So the deletion of record 2, also caused the deletion of record 3 because of the granted_by_id foreign key

与用户共享笔记的模型关联

1 个答案: