One to many relationships

Rails
1

I was trying to make one to many relationships - between professors
controller to rate_professors controller and used scaffold. it’s
giving me this error-

NoMethodError in RateProfessorsController#index
undefined method rate_professors' for nil:NilClass app/controllers/rate_professors_controller.rb:7:inindex’
Request

Parameters:
{“professor_id”=>“1”}

here are the codes for two controllers and index page–

class ProfessorsController < ApplicationController

GET /professors

GET /professors.json

def index
@professors = Professor.all
@rate_professors=RateProfessor.order(:lname)

respond_to do |format|
  format.html # index.html.erb
  format.json { render json: @professors }
end

end

GET /professors/1

GET /professors/1.json

def show
@professor = Professor.find(params[:id])

respond_to do |format|
  format.html # show.html.erb
  format.json { render json: @professor }
end

end

GET /professors/new

GET /professors/new.json

def new
@professor = Professor.new

respond_to do |format|
  format.html # new.html.erb
  format.json { render json: @professor }
end

end

GET /professors/1/edit

def edit
@professor = Professor.find(params[:id])
end

POST /professors

POST /professors.json

def create
@professor = Professor.new(params[:professor])

respond_to do |format|
  if @professor.save
    format.html { redirect_to @professor, notice: 'Professor was

successfully created.’ }
format.json { render json: @professor, status: :created,
location: @professor }
else
format.html { render action: “new” }
format.json { render json: @professor.errors,
status: :unprocessable_entity }
end
end
end

PUT /professors/1

PUT /professors/1.json

def update
@professor = Professor.find(params[:id])

respond_to do |format|
  if @professor.update_attributes(params[:professor])
    format.html { redirect_to @professor, notice: 'Professor was

successfully updated.’ }
format.json { head :no_content }
else
format.html { render action: “edit” }
format.json { render json: @professor.errors,
status: :unprocessable_entity }
end
end
end

DELETE /professors/1

DELETE /professors/1.json

def destroy
@professor = Professor.find(params[:id])
@professor.destroy

respond_to do |format|
  format.html { redirect_to professors_url }
  format.json { head :no_content }
end

end
end

For rate_professors controller:
class RateProfessorsController < ApplicationController

GET /rate_professors

GET /rate_professors.json

def index
@rate_professors = RateProfessor.all
professor = Professor.find(params[:professor_id])
@rate_professor =
@Professor.rate_professors.build([professor:professor])

@rate_professors
respond_to do |format|
format.html # index.html.erb
format.json { render json: @rate_professors }
end
end

GET /rate_professors/1

GET /rate_professors/1.json

def show
@rate_professor = RateProfessor.find(params[:id])

respond_to do |format|
  format.html # show.html.erb
  format.json { render json: @rate_professor }
end

end

GET /rate_professors/new

GET /rate_professors/new.json

def new

    @professor = Professor.find(params[:id])

 @rate_professor = RateProfessor.new

respond_to do |format|
  format.html # new.html.erb
  format.json { render json: @rate_professor }
end

end

GET /rate_professors/1/edit

def edit
@rate_professor = RateProfessor.find(params[:id])
end

POST /rate_professors

POST /rate_professors.json

def create
@professor = Professor.find(params[:id])
@rate_professor =
@Professor.rate_professors.build([professor:professor])

respond_to do |format|
  if @rate_professor.save
    format.html { redirect_to @rate_professor.professor, notice:

‘Rate professor was successfully created.’ }
format.json { render json: @rate_professor, status: :created,
location: @rate_professor }
else
format.html { render action: “new” }
format.json { render json: @rate_professor.errors,
status: :unprocessable_entity }
end
end
end

PUT /rate_professors/1

PUT /rate_professors/1.json

def update
@rate_professor = RateProfessor.find(params[:id])

respond_to do |format|
  if @rate_professor.update_attributes(params[:rate_professor])
    format.html { redirect_to @rate_professor, notice: 'Rate

professor was successfully updated.’ }
format.json { head :no_content }
else
format.html { render action: “edit” }
format.json { render json: @rate_professor.errors,
status: :unprocessable_entity }
end
end
end

DELETE /rate_professors/1

DELETE /rate_professors/1.json

def destroy
@rate_professor = RateProfessor.find(params[:id])
@rate_professor.destroy

respond_to do |format|
  format.html { redirect_to rate_professors_url }
  format.json { head :no_content }
end

end
end

index page

Listing rate_professors

<% @professor.rate_professors.each do |rate_professor| %>

<% end %>
Lname Helpfulness Explanation Technologyused Exams Homeworksorassignments Class Section Comments
<%= professor.lname %> <%= rate_professor.Helpfulness %> <%= rate_professor.Explanation %> <%= rate_professor.TechnologyUsed %> <%= rate_professor.Exams %> <%= rate_professor.HomeworksOrAssignments %> <%= rate_professor.Class %> <%= rate_professor.Section %> <%= rate_professor.comments %>

<%= link_to ‘New Rate professor’, new_rate_professor_path %>

2

On May 8, 8:21pm, Padmoja R. [email protected] wrote:

{“professor_id”=>“1”}

here are the codes for two controllers and index page–

def index
@rate_professors = RateProfessor.all
professor = Professor.find(params[:professor_id])
@rate_professor =
@Professor.rate_professors.build([professor:professor])

Ruby is telling you’re calling the rate_professors method on nil on
this line, so your first step should be to have a look at this like.
You’re calling it on @Professor which isn’t initialized, therefore
it’s nil. You’ve got the exact same mistake in a different action too.

Fred