has_many nested form with a has_one nested form within it

nested-attributes, nested-forms, ruby, ruby-on-rails

Solution

I solved my own issue here. What I did was, instead of building the answer model in the controller (which is impossible when you do not know how many questions are going to be made in the view), I built it when calling fields_for:

#CONTROLLER
class TestsController < ApplicationController

  #GET /tests/new
  def new
    @test = Test.new
    @questions = @test.questions.build
  end

end

#VIEW
<%= form_for @test do |f| %>
  <%= f.label :test_name %>
  <%= f.text_box :test_name %>
  <%= f.label :test_description %>
  <%= f.text_area :test_description %>
  <%= f.fields_for :questions do |questions_builder| %>
    <%= questions_builder.label :question %>
    <%= questions_builder.text_box :question %>
    <%= questions_builder.fields_for :answer, @questions.build_answer do |answers_builder| %>
      <%= answers_builder.label :answer %>
      <%= answers_builder.text_box :answer %>
    <% end %>
  <% end %>
  <%= link_to_add_fields 'New', f, :questions %>
<% end %>

This works because no matter how many question forms are being built on the view, a new answer specific to the question being built is built.

Problem

I am currently trying to make a form for a model, which has a dynamic number of nested models. I'm using Nested Forms (as described in RailsCasts 197). To make things even more complicated, each of my nested models has a `has_one` association with a third model, which I would also like to be added to the form. For any who are wondering about over normalization or an improper approach, this example is a simplified version of the problem I'm facing. In reality, things are slightly more complex, and this is the approach we've decided to take. Some example code to illustrate the problem below: ``` #MODELS class Test attr_accessible :test_name, :test_description, :questions_attributes has_many :questions accepts_nested_attributes_for :questions end class Question attr_accessible :question, :answer_attributes belongs_to :test has_one :answer accepts_nested_attributes_for :answer end class Answer attr_accessible :answer belongs_to :question end #CONTROLLER class TestsController < ApplicationController #GET /tests/new def new @test = Test.new @questions = @test.questions.build @answers = @questions.build_answer end end #VIEW <%= form_for @test do |f| %> <%= f.label :test_name %> <%= f.text_box :test_name %> <%= f.label :test_description %> <%= f.text_area :test_description %> <%= f.fields_for :questions do |questions_builder| %> <%= questions_builder.label :question %> <%= questions_builder.text_box :question %> <%= questions_builder.fields_for :answer do |answers_builder| %> <%= answers_builder.label :answer %> <%= answers_builder.text_box :answer %> <% end %> <% end %> <%= link_to_add_fields 'New', f, :questions %> <% end %> ``` This code example works fully for the first instance of Question. The issue occurs when another question is dynamically added to be created; the answer fields are not displayed. I believe this is because they are only built for the first question in the controller. Is there a way to achieve this using nested_attributes?

Original source