What is wrong in my script?(Survey Script)

Hi dear community,
I created a survey app which has questions and answers as radio buttons. So firstly i asked onstackoverflow(click-here). A good guy helped me but there is some issue in form. This my survey_controller:

     def new_response
    @survey = Survey.find(params[:id])
    @response = @survey.responses.build

    # now, the tricky part, you have to build the Answer objects so you can use the nested form later
    @survey.questions.each do |q|
      @response.answers.build question: q

def create_response
  @survey = Survey.find(params[:id])
  @response = @survey.build(response_params)
  @response.user = current_user

Here is my create_response form:

  = form_for @response, url: create_response_survey_path(@survey) do |f|
      - # you can iterate over all the answers already initialized
      = f.fields_for :answers do |ff|
         - # get the question from the current answer to show the title and options and a hidden_field with the      question id
        - q = ff.object.question

    = q.title
    = ff.hidden_field :question_id

    - # add the radios for each options for the question
    - q.options.each do |option|
      = label_tag do
        = ff.radio_button :option_id, option.id
        = option.title

  = f.submit 'Send'

My routes file:

Rails.application.routes.draw do

  devise_for :users
  	resources :surveys do 
    member do
      get :new_response
      get :create_response 
  root 'surveys#index'


It is showing error below when i try open the response form:

    undefined method `question' for nil:NilClass

    - q = ff.object.question

This is the repository link if you need check: Repository - Link

Thanks for all helps.

Is it a Slim template ? Honestly a do not see the point to not use ERB. It’s easier.
Templates are dinosaure, React and co. are the norm now.