Rails Instance Variables - ruby-on-rails

Question

I'm working on creating a survey app where surveys can have many questions and questions can have many surveys. What I'd like to do is on the survey show page display a button "Add new question" that allows a user to add a new question to that survey. So in my code I send the survey id like this:
<%= link_to "Add Question", new_question_path(:survey_id => #survey.id)%>
Then I can set #survey using the params I'm sending in my question controller. This is working fine in my :new method, but is throwing a nil error when I try to call in the :create method. I believe this is because a new instance of the controller is getting created which no longer has access to the :survey_id param I sent initially.
So I'm wondering if there is anyway to pass along the params to the next instance of the controller? Or is there a better way to send which survey should be set for that question? Is this something I could "save" in a hidden field? I thought about trying to save something in my model, but to save a question earlier would require me to remove the validations I have.
Here's my question_controller:
class QuestionsController < ApplicationController
before_action :set_question, only: [:show, :edit, :update, :destroy]
before_action :set_survey, only: [:new, :create]
# GET /questions
# GET /questions.json
def index
#questions = Question.all
end
# GET /questions/1
# GET /questions/1.json
def show
#answers = #question.answers
end
# GET /questions/new
def new
#question = Question.new
end
# GET /questions/1/edit
def edit
end
# POST /questions
# POST /questions.json
def create
#question = Question.new(question_params)
respond_to do |format|
if #question.save
#survey.questions << #question
format.html { redirect_to #question, notice: 'Question was successfully created.' }
format.json { render action: 'show', status: :created, location: #question }
else
format.html { render action: 'new' }
format.json { render json: #question.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /questions/1
# PATCH/PUT /questions/1.json
def update
respond_to do |format|
if #question.update(question_params)
format.html { redirect_to #question, notice: 'Question was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: #question.errors, status: :unprocessable_entity }
end
end
end
# DELETE /questions/1
# DELETE /questions/1.json
def destroy
#question.destroy
respond_to do |format|
format.html { redirect_to questions_url }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_question
#question = Question.find(params[:id])
end
def set_survey
#survey = Survey.find(params[:survey_id])
flash[:alert] = "Survey is " + #survey.to_s
end
# Never trust parameters from the scary internet, only allow the white list through.
def question_params
params.require(:question).permit(:title, :single_response, :surveys, :surveytizations)
end
end
And the form I'm creating the question with:
<%= form_for(#question) do |f| %>
<% if #question.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#question.errors.count, "error") %> prohibited this question from being saved:</h2>
<ul>
<% #question.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :title %><br>
<%= f.text_field :title %>
</div>
<div class="field">
<%= f.label :single_response %><br>
<%= f.check_box :single_response %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
Thanks! Any help is very much appreciated!
UPDATE:
I was able to work using Rails.cache.write/Rails.cache.read - How to pass values between controller methods
Is there anything wrong with doing it that way or is that the best route?

Answer 1

I think you need to store the survey_id in a hidden field. Then you can access it from the questions controller. In your view:
<%= form_for(#question) do |f| %>
<%= f.hidden_field :survey_id %>
#rest of form
You also might have to change your new action to something like this:
#question = Question.new(:survey_id => params[:survey_id])
If the questions always belongs to a survey it could be a good idea to nest the routes so that you always can check which survey you are working on.