Question

我有以下型号：

研究所
学生
教室
场

要求：

教室可以有很多课程。课程可以属于许多课堂。
教室里可以有很多学生。学生可以属于许多教室。
学生可以参加很多课程。一门课程可以属于很多学生。
学院有很多学生，很多教室和很多课程。

我正在尝试为上面创建关联：以下是准确的吗？

学院： has_and_belongs_to_many：学生| has_many：教室| has_many：courses
学生： has_and_belongs_to_many：机构| has_and_belongs_to_many：教室| has_many：课程| belongs_to：institute
课堂： has_and_belongs_to_many：学生| has_many：课程| belongs_to：institute
课程： has_and_belongs_to_many：学生| has_many：教室| belongs_to：institute

我如何在这里使用“通过”关系？

Answer 1

为Classroom关联和Cource关联

执行类似操作

运行：

ruby homework.rb

#homework.rb
require 'active_record'

`rm foobar.db`

class User < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: 'foobar.db'
  connection.create_table table_name, force: true do |t|
    t.string :name
  end
  connection.create_table :institutes_users, id: false do |t|
    t.integer :user_id
    t.integer :institute_id
  end

  has_and_belongs_to_many :institutes
end

class Institute < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: 'foobar.db'
  connection.create_table table_name, force: true do |t|
    t.string :name
  end
  connection.create_table :institutes_students, id: false do |t|
    t.integer :student_id
    t.integer :institute_id
  end

  has_and_belongs_to_many :users
  has_and_belongs_to_many :students
  has_many :classrooms
  has_many :courses
end

class Student < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: 'foobar.db'
  connection.create_table table_name, force: true do |t|
    t.string :name
  end
  connection.create_table :classrooms_students, id: false do |t|
    t.integer :student_id
    t.integer :classroom_id
  end

  has_and_belongs_to_many :institutes
  has_and_belongs_to_many :classrooms
  has_many :courses
end

class Classroom < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: 'foobar.db'
  connection.create_table table_name, force: true do |t|
    t.string :name
    t.references :institute
  end

  belongs_to :institute
  has_and_belongs_to_many :students
end

class Course < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: 'foobar.db'
  connection.create_table table_name, force: true do |t|
    t.string :name
    t.references :institute
    t.references :student
  end

  belongs_to :institute
  belongs_to :student
end
user = User.create!(name: 'John')
institute = Institute.create!(name: 'Harvard')
student = Student.create(name: 'Mary')
institute.users << user
institute.classrooms.create(name: '4th floor room')
institute.courses.create(name: 'IT')
institute.students << student
student.classrooms << Classroom.create(name: '5th froor room')
student.courses << Course.create(name: 'Biology')
p institute.users
p institute.classrooms
p institute.courses
p institute.students
p student.classrooms
p student.courses

使用Ruby On Rails设计模型

1 个答案: