has_many through access join table attribute in form - ruby-on-rails

Question

I have the following models:
class RandomExam < ActiveRecord::Base
has_many :random_exam_sections
has_many :sections, :through => :random_exam_sections
end
class Section < ActiveRecord::Base
has_many :random_exam_sections
has_many :random_exams, :through => :random_exam_sections
class RandomExamSection < ActiveRecord::Base
belongs_to :random_exam
belongs_to :section
end
The idea is to have certain configurations to create random exams, so this tables help to select which sections do you need and then also select the number of questions per section, here are the attributes of each table:
RandomExam: name(string), created_at(datetime), updated_at(datetime)
Section: name(string), created_at(datetime), updated_at(datetime)
RandomExamSection: random_exam_id(integer), section_id(integer), questions_number(integer)
As you can see the number of questions per section attribute is inside the RandomExamSections table and I want to access it in a form that is displayed from the RandomExam controller, here is my form:
<%= form_for (#random_exam) do |f| %>
<div class="row">
<div class="input-field col s12">
<%= f.label :name, 'Name' %>
<%= f.text_field :name, placeholder: 'Enter the name of the configuration' %>
</div>
</div>
<% #sections.each do |section| %>
<div class="row <%= dom_id(section) %>">
<div class="col s4">
<%= check_box_tag 'random_exam[section_ids][]', section.id,
#random_exam.section_ids.include?(section.id), id: dom_id(section), class: "section-checkbox #{dom_id(section)}" %>
<%= label_tag dom_id(section), (raw sanitize section.name, tags: %w(h2 p strong em a br b i small u ul ol li blockquote), attributes: %w(id class href)),
class: "name #{dom_id(section)}" %>
</div class="col s4">
<div>
<%= text_field_tag "random_exam[random_questions_numbers][#{section.id}][]", nil,
:placeholder => 'Enter the number of questions' %>
</div>
</div>
<% end %>
<div class="form-group">
<%= f.submit class: "btn waves-effect waves-light green" %>
</div>
<% end %>
My controller:
def create
#random_exam = RandomExam.new(random_exam_params)
if #random_exam.save
assign_random_questions_number
flash[:success] = 'Random configuration created successfully'
redirect_to #random_exam
else
flash.now[:danger] = #random_exam.errors.full_messages.to_sentence
render 'new'
end
def assign_random_questions_number
if params[:random_exam][:'random_questions_numbers'] == nil
return
end
params[:random_exam][:'section_ids'].each do |key, value|
record = RandomExamSection.search_ids(#random_exam.id, key)
record.each do |random_exam_section_record|
number_of_questions = params[:random_exam][:'random_questions_numbers'][key].first.to_i
random_exam_section_record.update(questions_number: number_of_questions)
end
end
end
I'm getting a TypeError: TypeError: nil is not a symbol nor a string when I update the record in the method assign_random_questions_number
This error even appears when I run this on the console
random = RandomExamSection.first
random.update(questions_number: 10)
Or when I run:
random = RandomExamSection.first
random.questions_number = 10
random.save
EDIT
I ended up deleting the association in RandomExamSection and recreating it inside 'assign_random_questions_number' with the questions_number
Thanks.

Answer 1

If you use nested_attributes you can do something like this:
#form
<h4>Selected exams</h4>
<%= f.fields_for :random_exam_sections do |b| %>
<%= b.hidden_field :section_id %>
<%= b.label :selected, b.object.section.name %>
<%= b.check_box :selected, { checked: !b.object.id.blank? } %>
<br>
<%= b.label :question_numbers %>
<%= b.text_field :questions_number %>
<% end %>
#RandomExamModel
class RandomExam < ApplicationRecord
has_many :random_exam_sections, inverse_of: :random_exam
has_many :sections, :through => :random_exam_sections
accepts_nested_attributes_for :random_exam_sections, reject_if: :is_not_selected
private
def is_not_selected(attr)
attr["selected"] == '0'
end
end
# RandomExam
class RandomExamSection < ApplicationRecord
belongs_to :random_exam
belongs_to :section
attr_accessor :selected
end
# Controller
# GET /random_exams/new
def new
#random_exam = RandomExam.new
#random_exam.random_exam_sections.build(Section.all.map{|s| {section_id: s.id}})
end
The idea basically is
- Build on controller the random_exam_sections to be selected
- Write a form that allows to you 'select' one option and assign the number
- Then, validate if the random_exam_section of a sections was selected (this why i made that `attr_accessor :selected`, i need a place to write if user select the exam_section)
- If was selected, save.
The trick here is build on the controller, then select on the view and validate the selected on the model. Here i made an example if you need help: https://github.com/afromankenobi/nested_attr_demo
To add sections when the random_exam_sections is already created you should probably use javascript. Maybe this railscasts can help you http://railscasts.com/episodes/196-nested-model-form-part-1