按班级对学生进行排序

Question

我有一个 Student 模型，其中包含 name:string 和 classroom:string 列。

我希望有一个页面列出每个班级的学生。

即
localhost:3000/students/1E1
本地主机：3000/学生/1E2
本地主机：3000/students/1E3
等

我似乎无法解决问题。这是我尝试自己开发的第一个 Rails 应用程序。但我真的被困住了！希望有人可以帮助我。

这段代码在我的students_controller.rb中

class StudentsController < ApplicationController
  def index
    @students = Student.all
  end

  def show
    @student = Student.find(params[:id])
  end


  def sort_by_class
    @student = Student.find(params[:id])
    @class = @student.classroom
  end

end

此代码在我的 show.html.erb 中

<h1>Students#show</h1>
<p>Find me in app/views/students/show.html.erb</p>


<%= @student.name %>
<%= @student.classroom%>

Answer 1

最好将“教室”作为模型并关联到学生：

m-n 学生和课堂协会：The has_and_belongs_to_many Association

在终端生成：

rails g model classroom number:string
rails g migration create_classrooms_student classroom:references student:references

models/student.rb

class Student < ActiveRecord::Base

  has_and_belongs_to_many :classrooms

end

models/classroom.rb

class Classroom < ActiveRecord::Base

  has_and_belongs_to_many :students

end

OR 1-n 学生和课堂协会：

在终端生成：

rails g model classroom number:string
rails g migration add_classroom_id_to_students classroom:references

models/student.rb

class Student < ActiveRecord::Base

  belongs_to :classroom

end

models/classroom.rb

class Classroom < ActiveRecord::Base

  has_many :students

end

两个例子的控制器

controllers/classrooms_controller.rb

class ClassroomsController < ApplicationController
  def index
    @classrooms = Classroom.all
  end

  def show
    @classroom = Classroom.find(params[:id])
  end
end

show.html.erb

<h1><%= @classroom.number %></h1>

<table>
  <thead>
  <tr>
    <th> Name </th>
  </tr>
  </thead>
  <tbody>
    <% @classroom.students.each do |student| %>
      <tr>
        <td><%= student.name %></td>
      </tr>
    <% end %>
  </tbody>
</table>

您的网址：

localhost:3000/classrooms/1E1

Answer 2

sort_by_class 是另一条路线还是要在索引中按类别排序？

假设教室是与学生（belongs_to :classroom）的关联，并且您在 Student 表中有一个 classroom_id 列，您可以执行 Student.order(:classroom_id) 之类的操作

Answer 3

或者简单的方法：

为教室创建新控制器

class ClassroomsController < ApplicationController
  def index
    @classrooms = Student.group(:classroom).pluck(:classroom)
  end

  def show
    @classroom = params[:id]
    @students = Student.where(params[:id])
  end
end

index.html.erb

<h1>Classrooms</h1>
<table>
  <% @classrooms.each do |classroom| %>
    <tr>
      <td><%= classroom %></td>
      <td><%= link_to(classroom, classroom_path(classroom)) %></td>
    </tr>
  <% end %>
</table>

show.html.erb

<h1>Classroom <%= @classroom %> Students</h1>
<table>
  <% @students.each do |student| %>
    <tr>
      <td><%= student.name %></td>
    </tr>
  <% end %>
</table>