CODEWITHSUNDEEP
ruby-on-railsmany-to-many
Asad
Asad

Reputation: 11

Display data from database in a many to many relationship

So I have two classes called Student and Classroom. It is a many to many relationship so my model is

class Student< ApplicationRecord
  has_many :student_classrooms
  has_many :classrooms, :through => :student_classrooms
end

class Classroom< ApplicationRecord
  has_many :student_classrooms
  has_many :students, :through => :student_classrooms
end

class StudentClassroom< ApplicationRecord
  belongs_to :student
  belongs_to :classroom
end

My controller in Student is

class CoursesController < ApplicationController

  def new
    @student = Student.new    
  end

  def create
    @student = Student.new(course_params)
    if @student.save
      flash[:success] = "Student created!"
      redirect_to @student
    end
  end

  def show
    @student = Student.find(params[:id])
    @name = @student.name
    #@classroom = Classroom.find_by(name: @name) <--
  end
  ...

end

My question is how do I get the classroom locations of a student and store it into a variable so I am able to show it on a webpage.

Upvotes: 1

Views: 186

Answers (2)

jvillian
jvillian

Reputation: 20263

Use:

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

That'll give you an ActiveRecord::Relation object which you can do further where statements on. Or, you could use it in your view to iterate and show all the student's classrooms.

Mark has it right, in your show.html.erb you can do something like: 

  <% @classrooms.each do |classroom| %>
    <%= classroom.name %>
  <% end %>

If you want something more than just the name (like maybe the classroom number), I would recommend going with a _classroom.html.erb partial. Which you would use something like:

  <% @classrooms.each do |classroom| %>
    <%= render partial: 'classroom', locals: {classroom: classroom} %>
  <% end %>

I would also recommend spending a few minutes and learning/converting to HAML. So, you can have a show.html.haml file that looks more like:

  - @classrooms.each do |classroom|
    .classroom-container{id: classroom.id}
      = render partial: 'classroom', locals: {classroom: classroom}

Or, for Mark's example:

%ul
  - @classrooms.each do |classroom|
    %li 
      = classroom.name

Isn't that much prettier? And, you save yourself all that hassle of typing out annoying erb syntax. And no having to remember to close tags! HAML is full of rainbows and smells like cotton candy!

Upvotes: 1

Mark
Mark

Reputation: 10998

In your show method:

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

Then in your app/views/students/show.html.erb file, you could do something like this:

<ul>
  <% @classrooms.each do |classroom| %>
    <li><%= classroom.name %></li>
  <% end %>
</ul>

This would print all the classroom names for the student you are viewing as an unordered list.

Upvotes: 0

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