同時設定IDのようなコールバックを定義する方法

Question

私のアプリケーションに企業やプロジェクトが含まれている場合、これらのモデルは次のように定義されています。

ActiveRecord::Schema.define(version: 20170927135313) do 

    create_table "companies", force: :cascade do |t| 
    t.string "name" 
    t.integer "high_price_company_id_id" 
    t.datetime "created_at", null: false 
    t.datetime "updated_at", null: false 
    t.index ["high_price_company_id_id"], name: "index_companies_on_high_price_company_id_id" 
    end 

    create_table "projects", force: :cascade do |t| 
    t.string "name" 
    t.integer "price" 
    t.integer "company_id" 
    t.datetime "created_at", null: false 
    t.datetime "updated_at", null: false 
    t.index ["company_id"], name: "index_projects_on_company_id" 
    end 

end 

は、外資系の高値企業レコードである。私はsaveを2度呼んでいます。しかし、それは少し無駄ですね。効率的なコールバックを定義する方法。私はsaveに一度だけ電話したいと思う。

2.3.3 :001 > company = Company.new 
=> #<Company id: nil, name: nil, high_price_company_id_id: nil, created_at: nil, updated_at: nil> 
2.3.3 :002 > 4.times {company.projects.new(price: rand(1..100))} 
=> 4 
2.3.3 :003 > company.save 
    (0.1ms) begin transaction 
    SQL (0.6ms) INSERT INTO "companies" ("created_at", "updated_at") VALUES (?, ?) [["created_at", "2017-09-27 15:12:54.852223"], ["updated_at", "2017-09-27 15:12:54.852223"]] 
    SQL (0.4ms) INSERT INTO "projects" ("price", "company_id", "created_at", "updated_at") VALUES (?, ?, ?, ?) [["price", 34], ["company_id", 1], ["created_at", "2017-09-27 15:12:54.856119"], ["updated_at", "2017-09-27 15:12:54.856119"]] 
    SQL (0.2ms) INSERT INTO "projects" ("price", "company_id", "created_at", "updated_at") VALUES (?, ?, ?, ?) [["price", 77], ["company_id", 1], ["created_at", "2017-09-27 15:12:54.859440"], ["updated_at", "2017-09-27 15:12:54.859440"]] 
    SQL (0.2ms) INSERT INTO "projects" ("price", "company_id", "created_at", "updated_at") VALUES (?, ?, ?, ?) [["price", 50], ["company_id", 1], ["created_at", "2017-09-27 15:12:54.862167"], ["updated_at", "2017-09-27 15:12:54.862167"]] 
    SQL (0.3ms) INSERT INTO "projects" ("price", "company_id", "created_at", "updated_at") VALUES (?, ?, ?, ?) [["price", 91], ["company_id", 1], ["created_at", "2017-09-27 15:12:54.863989"], ["updated_at", "2017-09-27 15:12:54.863989"]] 
    (2.8ms) commit transaction 
=> true 
2.3.3 :004 > max_price_proj = company.projects.maximum(:price) 
    (0.4ms) SELECT MAX("projects"."price") FROM "projects" WHERE "projects"."company_id" = ? [["company_id", 1]] 
=> 91 
2.3.3 :005 > company.high_price_company_id_id = max_price_proj 
=> 91 
2.3.3 :006 > company.save 
    (0.1ms) begin transaction 
    SQL (2.2ms) UPDATE "companies" SET "high_price_company_id_id" = ?, "updated_at" = ? WHERE "companies"."id" = ? [["high_price_company_id_id", 91], ["updated_at", "2017-09-27 15:13:30.411374"], ["id", 1]] 
    (2.7ms) commit transaction 
=> true 

Answer 1

私はあなたのFK high_price_company_id_idの名前は誤解を招くと思います。オプションの名前をhighest_priced_project_idに変更することもできます。

before_save do 
    self.highest_priced_project_id = self.projects.max_by(&:price).id 
end 

：

FKあなたは会社でのコールバックを定義することができることを更新するには