Ruby on rails - undefined method in show.html.erb - ruby-on-rails

Question

I am trying to display the name of the faculty instead of just the ID.
Everything else works except that part where I try to display the name of the faculty. I get an error saying "undefined method" .
I know I am doing something wrong, but I cannot figure it out at all even though I have been looking at this for hours. I am a completely beginner and I would really appreciate your help.
Thank you.
show.html.erb
<p id="notice"><%= notice %></p>
<!-- notice is a ruby method, and its results comes here inside the tags
used when you want the errow page to show on the next page -->
<p>
<strong>Name:</strong>
<%= #student.name %>
</p>
<p>
<strong>Faculty:</strong>
<%= #student.faculty_id %>
<%= #name.faculty_id %>
</p>
<strong>Grade:</strong>
<%= #student.grade%>
</p>
<%= link_to 'Edit', edit_student_path(#student) %> |
<%= link_to 'Back', students_path %>
student.rb
class Student < ActiveRecord::Base
belongs_to :faculty
end
class Name < ActiveRecord::Base
belongs_to :faculty
end
faculty.rb
class Faculty < ActiveRecord::Base
has_many :student
# belongs_to :faculty
has_many :name
end
This is my students_controler.rb
class StudentsController < ApplicationController
before_action :set_student, only: [:show, :edit, :update, :destroy]
# GET /students
# GET /students.json
def index
#students = Student.all
end
# GET /students/1
# GET /students/1.json
def show
end
# GET /students/new
def new
#student = Student.new
end
# GET /students/1/edit
def edit
end
# POST /students
# POST /students.json
def create
#student = Student.new(student_params)
respond_to do |format|
if #student.save
format.html { redirect_to #student, notice: 'Student was successfully created.' }
format.json { render :show, status: :created, location: #student }
else
format.html { render :new }
format.json { render json: #student.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /students/1
# PATCH/PUT /students/1.json
def update
respond_to do |format|
if #student.update(student_params)
format.html { redirect_to #student, notice: 'Student was successfully updated.' }
format.json { render :show, status: :ok, location: #student }
else
format.html { render :edit }
format.json { render json: #student.errors, status: :unprocessable_entity }
end
end
end
# DELETE /students/1
# DELETE /students/1.json
def destroy
#student.destroy
respond_to do |format|
format.html { redirect_to students_url, notice: 'Student was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_student
#student = Student.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def student_params
params.require(:student).permit(:name, :faculty_id)
end
end
The error is undefined method `faculty_id' for nil:NilClass

Answer 1

I am trying to display the name of the faculty instead of just the ID
Since you're a beginner, let me explain it for you...
--
You're currently calling #student.faculty_id
This is the foreign_key of the #student object -- the identifier which links this student object to the appropriate faculty object.
In short, it means that this attribute is a part of the student schema -- you want one which is part of the faculty schema. Thus, you either need to use delegate to call the name attribute from faculty, or just call it directly:
#student.faculty.name
There are deeper problems with your model associations.
The above is how they should be set up:
#app/models/student.rb
class Student < ActiveRecord::Base
belongs_to :faculty
end
#app/models/faculty.rb
class Faculty < ActiveRecord::Base
has_many :students
end
The above will allow you to call the following:
#app/controllers/students_controller.rb
class StudentsController < ApplicationController
def show
#student = Student.find params[:id]
end
end
#app/views/students/view.html.erb
<%= #student.faculty.name %>
You must remember that Rails works on top of a relational database. This works by allowing you to call related objects by virtue of their foreign key.
I can explain more if required.

Answer 2

<%= #name.faculty_id %> won't work.
In your controller eager load the faculty
def show
#student = Student.includes(:faculty)
end
Either do
<% if #student.faculty.present? %>
<%= #student.faculty.name %>
<% end %>
or you could get the faculty in the controller and assign it to a variable
def show
#student = Student.includes(:faculty)
#faculty = #student.faculty
end
Then you can use that
<% if #faculty.present? %>
<%= #faculty.name %>
<% end %>

Answer 3

Error which I see is
class Faculty < ActiveRecord::Base
has_many :student
# belongs_to :faculty
has_many :name
end
Should be
class Faculty < ActiveRecord::Base
has_many :students
# belongs_to :faculty
has_many :names
end
I don't know your error due to this is or not but has_many is not with singular form