如何在整个rails活动记录关联链中取消特定模型的默认范围？

Question

我试图解决以下问题。我有三个模型：用户has_many相机has_many录音。

class AddTables < ActiveRecord::Migration
  def change
    create_table :users
    create_table :cameras do |t|
      t.references :user, null: false, foreign_key: true
      t.timestamp :archived_at, index: true
    end
    create_table :recordings do |t|
      t.references :camera, null: false, foreign_key: true
      t.timestamp :archived_at, index: true
    end
  end
end

相机和录制具有特殊字段“archived_at”，用于将记录标记为已删除（软删除）。我想让用户#记录查看所有摄像机（任何Camera.archived_at），但同时，我希望它只查看弧形记录（Recording.aarchived_at==nil）。我试过几次，但都没有成功。

===情况1 ===

class User < ActiveRecord::Base
  has_many :cameras, -> { unscope where: :archived_at }
  has_many :recordings, through: :cameras
end

class Camera < ActiveRecord::Base
  default_scope { where(archived_at: nil) }

  belongs_to :user
  has_many :recordings
end

class Recording < ActiveRecord::Base
  default_scope { where(archived_at: nil) }

  belongs_to :camera
end

irb（主）：013:0

===情况2===

class User < ActiveRecord::Base
  has_many :cameras, -> { unscope where: :archived_at }
  has_many :recordings, through: :cameras
end

class Camera < ActiveRecord::Base
  default_scope { where(cameras: {archived_at: nil}) }

  belongs_to :user
  has_many :recordings
end

class Recording < ActiveRecord::Base
  default_scope { where(recordings: {archived_at: nil}) }

  belongs_to :camera
end

irb（主）：013:0

===情况3 ===

class User < ActiveRecord::Base
  has_many :cameras, -> { unscope where: {cameras: :archived_at} }
  has_many :recordings, through: :cameras
end

class Camera < ActiveRecord::Base
  default_scope { where(cameras: {archived_at: nil}) }

  belongs_to :user
  has_many :recordings
end

class Recording < ActiveRecord::Base
  default_scope { where(recordings: {archived_at: nil}) }

  belongs_to :camera
end

irb(主):016:0

Answer 1

试试这个：

< code>user.rb:

class User < ApplicationRecord
    has_many :cameras
    has_many :recordings, -> { unscope(where: :archived_at).where(recordings: {archived_at: nil}) }, through: :cameras
end

相机.rb：

class Camera < ApplicationRecord
    default_scope { where(archived_at: nil) }
    belongs_to :user
    has_many :recordings
end

录音.rb：

class Recording < ApplicationRecord
    belongs_to :camera
    default_scope { where(archived_at: nil) }
end

以下是输出查询:

irb(main):088:0> User.first.recordings
User Load (0.2ms)  SELECT  "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ?  [["LIMIT", 1]]
Recording Load (0.1ms)  SELECT "recordings".* FROM "recordings" INNER JOIN "cameras" ON "recordings"."camera_id" = "cameras"."id" WHERE "cameras"."user_id" = ? AND "recordings"."archived_at" IS NULL  [["user_id", 1]]