How to save nested form data in Rails?

I have this data inside my foods and drinks table:

Foods table

ID  | Name
------------
1   | Rojak
2   | Lemang

Drinks table

ID  | Name
------------
1   | Barli
2   | Sirap

My model relationship is:

class Survey < ActiveRecord::Base
  has_many :questions
  accepts_nested_attributes_for :questions, allow_destroy: true
end
class Question < ActiveRecord::Base
  belongs_to :survey
  has_many :answers
  accepts_nested_attributes_for :answers, allow_destroy: true
end
class Answer < ActiveRecord::Base
  belongs_to :question
  has_many :foods
  has_many :drinks
  accepts_nested_attributes_for :foods, :drinks
end
class Food < ActiveRecord::Base
    belongs_to :answer
end
class Drink < ActiveRecord::Base
    belongs_to :answer
end

And this is my _form.html.erb file inside app/views/surveys:

<%= form_for @survey do |f| %>
  <% if @survey.errors.any? %>
    <div class="error_messages">
      <h2><%= pluralize(@survey.errors.count, "error") %> prohibited this survey from being saved:</h2>
      <ul>
      <% @survey.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>

  </div>
  <br>
  <%= f.fields_for :questions do |f| %>
    <fieldset>
    <%= f.label :content, "Question" %><br />
    <%= f.text_area :content %><br />

    <% Food.all.each do |fd| %>
    <fieldset>
      <%= f.fields_for :answers do |f| %>
        <%= f.text_field :name, :value => fd.name %>
        <%= f.number_field :quantity %>
      <% end %> <br>
    </fieldset>
    <% end %>

  </fieldset>
  <br>
  <% end %>
  <br>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

What I'm trying to do is:

1. List all foods name and drinks name inside foods and drinks fieldset
2. Give each of the foods and drinks a quantity (this quantity column is inside answers table)
3. Save and update it

But I got no luck. When I'm try to load the edit view (the form), I managed to list all of the foods name. But, I've no idea how to list all of the drinks name in its own fieldset.

I try to make it like this but it didn't work:

<% if :content == "Foods" %>
  <%= #loads foods %>
<% else %>
  <%= #loads drinks %>
<% end %>

And, when I try to save the foods/drinks name and its quantity, it didn't work too.

Demo:

How to fix this problem?

Note:

This is update method inside surveys_controller:

def update
    if @survey.update(survey_params)
      redirect_to @survey, notice: "Successfully updated survey."
    else
      render :edit
    end
  end

...

def survey_params
    params.require(:survey).permit(:name, questions_attributes: [:id, :_destroy, :content, answers_attributes: [:id, :_destroy, :content, :quantity]])
  end

Update:

This is my show.html.erb

<h1><%= @survey.name %></h1>

<ul class="questions">
<% @survey.questions.each do |question| %>
  <li>
    <%= question.content %>
    <ol class="answers">
      <% question.answers.each do |answer| %>
        <li><%= answer.content %> (<%= answer.quantity %>)</li>
      <% end %>
    </ol>
  </li> <br>
<% end %>
</ul>

<%= link_to 'Edit', edit_survey_path(@survey) %> |
<%= link_to 'Back to Surveys', surveys_path %>