has_oneな関連をaccepts_nested_attributes_forしている場合にattributesで代入した場合idが無いとdestroyされる

これを知らなくて小一時間ハマったので、メモ

環境

• Rails 5.2.1

結論から言うと

• has_oneなfieldをaccepts_nested_attributes_forする場合は、 update_only: true にしておいた方が安全かもしれない

ActiveRecord::NestedAttributes::ClassMethods accepts_nested_attributes_for(*attr_names)

現象

以下のようなテーブルとモデルがあったとする。

class CreateUsers < ActiveRecord::Migration[5.2]
  def change
    create_table :users do |t|
      t.string :name

      t.timestamps
    end
  end
end

class CreateUserProfiles < ActiveRecord::Migration[5.2]
  def change
    create_table :user_profiles do |t|
      t.string :avatar
      t.belongs_to :user

      t.timestamps
    end
  end
end

class User < ApplicationRecord
  has_one :user_profile, dependent: :destroy
  accepts_nested_attributes_for :user_profile
end

class UserProfile < ApplicationRecord
  belongs_to :user
end

User : UserProfile が has_one つまり 1 : 1 な関係で存在している。

とりあえず、Userのデータを作成する

[13] pry(main)> User.create(name: "test", user_profile_attributes: { avatar: "http://hoge.com" })
   (0.1ms)  begin transaction
  User Create (9.7ms)  INSERT INTO "users" ("name", "created_at", "updated_at") VALUES (?, ?, ?)  [["name", "test"], ["created_at", "2018-09-19 02:31:31.405308"], ["updated_at", "2018-09-19 02:31:31.405308"]]
  UserProfile Create (1.6ms)  INSERT INTO "user_profiles" ("avatar", "user_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["avatar", "http://hoge.com"], ["user_id", 3], ["created_at", "2018-09-19 02:31:31.416808"], ["updated_at", "2018-09-19 02:31:31.416808"]]
   (8.3ms)  commit transaction
=> #<User:0x0000560a59d8a630 id: 3, name: "test", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00>

[14] pry(main)> u = User.last
  User Load (2.7ms)  SELECT  "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ?  [["LIMIT", 1]]
=> #<User:0x0000560a598f3c70 id: 3, name: "test", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00>

[15] pry(main)> u.user_profile
  UserProfile Load (2.5ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a59843500 id: 2, avatar: "http://hoge.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00>

User#attributes で idなし の user_profile_attributes をセットする

[16] pry(main)> u.attributes = { user_profile_attributes: { avatar: "http://xxxxxxxx.com" } }
   (0.1ms)  begin transaction
  UserProfile Destroy (9.2ms)  DELETE FROM "user_profiles" WHERE "user_profiles"."id" = ?  [["id", 2]]
   (5.7ms)  commit transaction
=> {:user_profile_attributes=>{:avatar=>"http://xxxxxxxx.com"}}

attributesに代入しただけで、saveしてないのに、UserProfileはdestroyされている

saveしてないので、あたらしいUserProfileのidはnilになっている

[17] pry(main)> u.user_profile
=> #<UserProfile:0x0000560a597113a8 id: nil, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: nil, updated_at: nil>

当然、reloadすると、user_profileはnilになる

[18] pry(main)> u.reload.user_profile
  User Load (2.5ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 3], ["LIMIT", 1]]
  UserProfile Load (0.6ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> nil

[21] pry(main)> UserProfile.count
   (2.5ms)  SELECT COUNT(*) FROM "user_profiles"
=> 0

不用意にrails consoleでattributesの代入をして、データを失うという悲劇。

どういう時に困るのか？

User側にvalidationエラーがあったりして、saveできない時。

通常、createやupdateメソッドを使っていれば、困らないかもしれない。

class User < ApplicationRecord
  has_one :user_profile, dependent: :destroy
  accepts_nested_attributes_for :user_profile

  validates :name, length: { minimum: 10 }
end

User#name に10文字以上のvalidationを追加した。

attributesでセットした場合

[29] pry(main)> u = User.last
  User Load (0.8ms)  SELECT  "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ?  [["LIMIT", 1]]
=> #<User:0x0000560a5ab7b2a8 id: 3, name: "test", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00>

[30] pry(main)> u.user_profile
  UserProfile Load (1.1ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x00007f698c867638 id: 4, avatar: "http://xxxxxxxx.co", user_id: 3, created_at: Wed, 19 Sep 2018 02:41:30 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:41:30 UTC +00:00>

[31] pry(main)> u.attributes = { name: "hoge" , user_profile_attributes: { avatar: "http://hoge.com" } }
   (0.1ms)  begin transaction
  UserProfile Destroy (7.7ms)  DELETE FROM "user_profiles" WHERE "user_profiles"."id" = ?  [["id", 4]]
   (6.7ms)  commit transaction
=> {:name=>"hoge", :user_profile_attributes=>{:avatar=>"http://hoge.com"}}

[32] pry(main)> u.save
   (0.1ms)  begin transaction
   (0.0ms)  rollback transaction
=> false

[34] pry(main)> u.errors
=> #<ActiveModel::Errors:0x00007f698c7e5c50
 @base=#<User:0x0000560a5ab7b2a8 id: 3, name: "hoge", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00>,
 @details={:name=>[{:error=>:too_short, :count=>10}]},
 @messages={:name=>["is too short (minimum is 10 characters)"]}>

[35] pry(main)> u.reload.user_profile
  User Load (3.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 3], ["LIMIT", 1]]
  UserProfile Load (0.6ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> nil

こうなるので、Userがsave出来ない状態で、UserProfileが削除されてしまう。

if user.save
  …
else
  render :edit
end

のように、例外が発生しない状態だとrollbackも出来ず、データが消えてしまう。

updateで更新する場合

[40] pry(main)> u = User.last
  User Load (2.3ms)  SELECT  "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ?  [["LIMIT", 1]]
=> #<User:0x00007f698c012348 id: 3, name: "1234567890", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>

[41] pry(main)> u.user_profile
  UserProfile Load (2.5ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a5aa0b670 id: 5, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>

[42] pry(main)> u.update name: "1234", user_profile_attributes: { avatar: "http://xxxxxxxx.com" }
   (0.1ms)  begin transaction
  UserProfile Destroy (7.7ms)  DELETE FROM "user_profiles" WHERE "user_profiles"."id" = ?  [["id", 5]]
   (3.2ms)  rollback transaction
=> false

[43] pry(main)> u.user_profile
=> #<UserProfile:0x0000560a5a9ace68 id: nil, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: nil, updated_at: nil>

[44] pry(main)> u.reload.user_profile
  User Load (1.9ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 3], ["LIMIT", 1]]
  UserProfile Load (0.5ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a5a733510 id: 5, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>

updateメソッド実行時に、transactionがrollbackされているのがわかる。
u.user_profileには新しいレコードのデータがセットされているが、
destroyがロールバックされているので、reloadすると、元に戻る

ただし、ここでこんなことをすると、ゴミデータが出来てしまう。

[45] pry(main)> u.update name: "1234", user_profile_attributes: { avatar: "http://x.com" }
   (0.1ms)  begin transaction
  UserProfile Destroy (8.2ms)  DELETE FROM "user_profiles" WHERE "user_profiles"."id" = ?  [["id", 5]]
   (3.7ms)  rollback transaction
=> false

[46] pry(main)> u.user_profile
=> #<UserProfile:0x0000560a5a669bc0 id: nil, avatar: "http://x.com", user_id: 3, created_at: nil, updated_at: nil>

[47] pry(main)> u.user_profile.save
   (0.1ms)  begin transaction
  UserProfile Create (10.5ms)  INSERT INTO "user_profiles" ("avatar", "user_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["avatar", "http://x.com"], ["user_id", 3], ["created_at", "2018-09-19 02:58:50.666477"], ["updated_at", "2018-09-19 02:58:50.666477"]]
   (7.3ms)  commit transaction
=> true

[48] pry(main)> u.reload.user_profile
  User Load (2.3ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 3], ["LIMIT", 1]]
  UserProfile Load (0.6ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a5a394d00 id: 5, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>

[49] pry(main)> UserProfile.all
  UserProfile Load (2.4ms)  SELECT "user_profiles".* FROM "user_profiles"
=> [#<UserProfile:0x0000560a59feac68 id: 5, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>,
 #<UserProfile:0x0000560a59feab00 id: 6, avatar: "http://x.com", user_id: 3, created_at: Wed, 19 Sep 2018 02:58:50 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:58:50 UTC +00:00>]

ただ、これはUnique制約をちゃんと入れておけば回避できるかと。

原因調査してみる

• accepts_nested_attributes_for のソースを見てみる
  • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/nested_attributes.rb#L333-L354
  • generate_association_writer でメソッドを定義してるっぽい
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/nested_attributes.rb#L369-L376
  • 定義されたメソッドの中で、今回のケースは has_one なので assign_nested_attributes_for_one_to_one_association　が呼ばれる
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/nested_attributes.rb#L407-L437
  • この中で、今回のケースでは、 build_user_profile が呼ばれていた
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/nested_attributes.rb#L429-L431
• has_one な関連のbuildメソッドはなにをしているのか？
  • ActiveRecord::Associations::SingularAssociation#build が呼ばれているはず
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/singular_association.rb#L20-L24
  • ここで、 set_new_record している。（あやしい）
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/singular_association.rb#L60-L62
    • replace … なんとなくニュアンス的にここあやしい
  • SingularAssociation#replaceは実装されていないので、HasOneの方をみる
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/singular_association.rb#L56-L58
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/has_one_association.rb#L26-L50
  • remove_target!(options[:dependent]) してる
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/has_one_association.rb#L37
  • 今回のケースでは dependent: :destoy をUser#user_profileに設定して居たため、ここでdestroyされていた
    • https://github.com/rails/rails/blob/5-2-1/activerecord/lib/active_record/associations/has_one_association.rb#L80-L97

すっきりした

対応策

さきに書いてしまったけど、accepts_nested_attributes_for のオプションに update_only: true を入れることで、既存のレコードを更新する事ができる

class User < ApplicationRecord
  has_one :user_profile, dependent: :destroy
  accepts_nested_attributes_for :user_profile, update_only: true

  validates :name, length: { minimum: 10 }
end

[53] pry(main)> u = User.last
  User Load (1.1ms)  SELECT  "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ?  [["LIMIT", 1]]
=> #<User:0x0000560a5950e740 id: 3, name: "1234567890", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>

[54] pry(main)> u.user_profile
  UserProfile Load (0.7ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a5942b1c0 id: 7, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00, updated_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00>

[55] pry(main)> UserProfile.all
  UserProfile Load (2.9ms)  SELECT "user_profiles".* FROM "user_profiles"
=> [#<UserProfile:0x0000560a593b1ac8 id: 7, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00, updated_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00>]

[56] pry(main)> u.attributes =  {name: "1234", user_profile_attributes: { avatar: "http://x.com" }}
=> {:name=>"1234", :user_profile_attributes=>{:avatar=>"http://x.com"}}

[57] pry(main)> u.user_profile
=> #<UserProfile:0x0000560a5942b1c0 id: 7, avatar: "http://x.com", user_id: 3, created_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00, updated_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00>

[59] pry(main)> u.user_profile.changed?
=> true

[60] pry(main)> u.save
   (0.1ms)  begin transaction
   (0.1ms)  rollback transaction
=> false

[61] pry(main)> u.errors
=> #<ActiveModel::Errors:0x00007f698c8a6bd0
 @base=#<User:0x0000560a5950e740 id: 3, name: "1234", created_at: Wed, 19 Sep 2018 02:31:31 UTC +00:00, updated_at: Wed, 19 Sep 2018 02:53:35 UTC +00:00>,
 @details={:name=>[{:error=>:too_short, :count=>10}]},
 @messages={:name=>["is too short (minimum is 10 characters)"]}>

[62] pry(main)> u.user_profile
=> #<UserProfile:0x0000560a5942b1c0 id: 7, avatar: "http://x.com", user_id: 3, created_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00, updated_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00>

[63] pry(main)> u.reload.user_profile
  User Load (1.8ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 3], ["LIMIT", 1]]
  UserProfile Load (0.6ms)  SELECT  "user_profiles".* FROM "user_profiles" WHERE "user_profiles"."user_id" = ? LIMIT ?  [["user_id", 3], ["LIMIT", 1]]
=> #<UserProfile:0x0000560a5abe6be8 id: 7, avatar: "http://xxxxxxxx.com", user_id: 3, created_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00, updated_at: Wed, 19 Sep 2018 03:34:16 UTC +00:00>

• attributesに代入したタイミングで、destroyされなくなった
• 既存のUserProfileが更新されている
  • changed?がtrue
• validationエラーでsaveされない
  • reloadすれば元に戻る