Question

在我的包含公司和项目的应用程序中，这些模型的定义如下。

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

high_price_company_id_id是外键，表示高价公司记录。我打电话给save两次。但是，这有点浪费，不是吗？如何定义有效的回拨。我只想打save一次。

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

我认为您的FK high_price_company_id_id的名称具有误导性。一个选项是将其重命名为highest_priced_project_id。

要更新该FK，您可以在公司中定义回调：

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

如何定义回调，如同时设置id

1 个答案: