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我是 Rails 初学者，为了学习它，我正在构建一个简单的时间跟踪应用程序。我想用来自许多具有嵌套信息的表的大量信息来填充管理员的仪表板。

查询数据库以请求一家公司的所有数据以查看所有客户、项目、任务、调整和会议记录的仪表板的最佳实践是什么？

以下是数据的结构方式：

公司拥有_众多客户

客户所属_公司有_许多项目

项目属于_to client has_many tasks

任务属于_to 项目 has_many 分钟

分belongs_to任务

这种数据结构可能真的很糟糕。我不知道。

数据的示例视图：

动视
-- 网站重新设计
--- 开发
---- 100 分钟

我从这个开始，但我很漂亮，但它可能完全倒退（用户属于公司）：

    @clients = Client.find_all_by_company_id(current_user.company_id)
    @clients.each do |client| 

        project = Project.find_all_by_client_id(client.id)
        puts project.name

        project.each do |project|

            task = Task.find_all_by_project_id(project.id)
            puts task.name

        end
    end

我想这个问题也可以问：有没有一本好书或资源可以完整描述 Rails ActiveRecord 最佳实践？

4

3 回答 3

1

这会产生与您相同的结果

@clients = current_user.company.clients
@clients.each do |client| 
    projects = client.projects

    # puts project.name # makes no sense here

    projects.each do |project|

        project.tasks.each do |task|
            puts task.name
        end
    end
end
于 2012-09-12T04:55:06.290 回答
1

使用该includes方法急切地加载关联。

指南中的示例

Category.includes(:posts => [{:comments => :guest}, :tags]).find(1)

根据你说的，应该是：

require 'active_record'
require 'logger'

# =====  Config  =====
ActiveRecord::Base.establish_connection adapter: 'sqlite3', database: ':memory:'
ActiveRecord::Base.logger = Logger.new $stdout
ActiveSupport::LogSubscriber.colorize_logging = false

# =====  Schema  =====
ActiveRecord::Schema.define do
  self.verbose = false

  create_table :clients do |t|
    t.string  :name
    t.integer :company_id
  end

  create_table :companies do |t|
    t.string :name
  end

  create_table :projects do |t|
    t.string  :name
    t.integer :client_id
  end

  create_table :tasks do |t|
    t.string  :name
    t.integer :project_id
  end

  create_table :minutes do |t|
    t.integer :quantity
    t.integer :task_id
  end
end

# =====  Classes  =====
class Company < ActiveRecord::Base
  has_many :clients
end

class Client < ActiveRecord::Base
  belongs_to :company
  has_many   :projects
end

class Project < ActiveRecord::Base
  belongs_to :client
  has_many   :tasks
end

class Task < ActiveRecord::Base
  belongs_to :project
  has_many   :minutes
end

class Minute < ActiveRecord::Base
  belongs_to :task
end

# =====  Data  =====
Company.create! name: 'Activision' do |company|
  company.clients.build name: 'Robert Kotick' do |client|
    client.projects.build name: 'Website Redesign' do |project|
      project.tasks.build name: 'Development' do |task|
        task.minutes.build quantity: 100
      end
    end
  end
end

# =====  Querying and displaying  =====
company = Company.find_by_name 'Activision'
clients = Client.includes(projects: {tasks: :minutes}).where(company_id: company.id)

print "\n----- The query makes four requests, regardless of how much data you have. -----\n\n"
clients.inspect # do this to force loading since AR queries are lazy

print "\n----- some representation of the data (notice no queries while iterating through) -----\n\n"
clients.each do |client|
  puts client.name
  client.projects.each do |project|
    puts "-- #{project.name}"
    project.tasks.each do |task|
      puts "--- #{task.name}"
      task.minutes.each do |minute|
        puts "---- #{minute.quantity}"
      end
    end
  end
end

# =====  Output =====

# >> D, [2012-09-12T00:01:42.755414 #72855] DEBUG -- :    (0.7ms)  select sqlite_version(*)
# >> D, [2012-09-12T00:01:42.755890 #72855] DEBUG -- :    (0.2ms)  CREATE TABLE "clients" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255), "company_id" integer) 
# >> D, [2012-09-12T00:01:42.756327 #72855] DEBUG -- :    (0.1ms)  CREATE TABLE "companies" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255)) 
# >> D, [2012-09-12T00:01:42.756728 #72855] DEBUG -- :    (0.1ms)  CREATE TABLE "projects" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255), "client_id" integer) 
# >> D, [2012-09-12T00:01:42.757122 #72855] DEBUG -- :    (0.1ms)  CREATE TABLE "tasks" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255), "project_id" integer) 
# >> D, [2012-09-12T00:01:42.757531 #72855] DEBUG -- :    (0.1ms)  CREATE TABLE "minutes" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "quantity" integer, "task_id" integer) 
# >> D, [2012-09-12T00:01:42.906877 #72855] DEBUG -- :    (0.0ms)  begin transaction
# >> D, [2012-09-12T00:01:42.909242 #72855] DEBUG -- :   SQL (0.5ms)  INSERT INTO "companies" ("name") VALUES (?)  [["name", "Activision"]]
# >> D, [2012-09-12T00:01:42.934937 #72855] DEBUG -- :   SQL (24.7ms)  INSERT INTO "clients" ("company_id", "name") VALUES (?, ?)  [["company_id", 1], ["name", "Robert Kotick"]]
# >> D, [2012-09-12T00:01:42.936110 #72855] DEBUG -- :   SQL (0.1ms)  INSERT INTO "projects" ("client_id", "name") VALUES (?, ?)  [["client_id", 1], ["name", "Website Redesign"]]
# >> D, [2012-09-12T00:01:42.937001 #72855] DEBUG -- :   SQL (0.1ms)  INSERT INTO "tasks" ("name", "project_id") VALUES (?, ?)  [["name", "Development"], ["project_id", 1]]
# >> D, [2012-09-12T00:01:42.937767 #72855] DEBUG -- :   SQL (0.1ms)  INSERT INTO "minutes" ("quantity", "task_id") VALUES (?, ?)  [["quantity", 100], ["task_id", 1]]
# >> D, [2012-09-12T00:01:42.938005 #72855] DEBUG -- :    (0.0ms)  commit transaction
# >> D, [2012-09-12T00:01:42.939882 #72855] DEBUG -- :   Company Load (0.1ms)  SELECT "companies".* FROM "companies" WHERE "companies"."name" = 'Activision' LIMIT 1
# >> 
# >> ----- The query makes four requests, regardless of how much data you have. -----
# >> 
# >> D, [2012-09-12T00:01:42.940458 #72855] DEBUG -- :   Client Load (0.1ms)  SELECT "clients".* FROM "clients" WHERE "clients"."company_id" = 1
# >> D, [2012-09-12T00:01:42.943272 #72855] DEBUG -- :   Project Load (0.1ms)  SELECT "projects".* FROM "projects" WHERE "projects"."client_id" IN (1)
# >> D, [2012-09-12T00:01:42.943919 #72855] DEBUG -- :   Task Load (0.1ms)  SELECT "tasks".* FROM "tasks" WHERE "tasks"."project_id" IN (1)
# >> D, [2012-09-12T00:01:42.944520 #72855] DEBUG -- :   Minute Load (0.1ms)  SELECT "minutes".* FROM "minutes" WHERE "minutes"."task_id" IN (1)
# >> 
# >> ----- some representation of the data (notice no queries while iterating through) -----
# >> 
# >> Robert Kotick
# >> -- Website Redesign
# >> --- Development
# >> ---- 100

这是一个可怕的违反得墨忒耳法则的行为，如果这些东西在任何时候发生变化，无论是结构还是命名，我们都必须修复这个代码。如果不引入大量抽象，我不确定如何处理这个问题。

关于一本书，有很多，但老实说，我认为 Rails 世界还没有弄清楚什么是最佳 ActiveRecord 实践（事实上，社区中有很大一部分人认为几乎所有 ActiveRecord 实践都很糟糕——我大部分时间都在那个营地）。

但是，如果您想要上面提到的用于#includes急切加载关联的内容，那么指南是查找此类信息的好地方。我也很喜欢这个博客和视频。

于 2012-09-12T05:02:54.320 回答
0

尝试类似的东西

 Client.includes(
                      :company =>{:projects=>:tasks})

以上所有内容都应连接（通过 has_one、has_many、belongs_to）希望这会有所帮助！

于 2012-09-12T05:11:13.803 回答