Nested form update action producing duplicate results - ruby-on-rails

Question

During the update action of a nested form, instead of updating the current nested records, it seems to create new nested records.
This is what my controller looks like :
class ApplicationsController < ApplicationController
before_filter :set_user_and_job
def new
job = params[:job_id]
#application = Application.build(job)
end
def create
#application = Application.new(application_params)
#application.save
redirect_to root_url, :notice => "You have now applied!"
end
def edit
#application = Application.find(params[:id])
#answers = []
#job.questions.each do |question|
#application.answers.each do |answer|
#answers << answer if answer.question_id == question.id
end
end
end
def update
#application = Application.find(params[:id])
#application.update_attributes(application_params)
redirect_to root_url, :notice => "You have updated your application!"
end
def destroy
Application.find(params[:id]).destroy
flash[:success] = "Application Deleted."
redirect_to root_url
end
def show
#application = Application.find(params[:id])
#answers = []
#job.questions.each do |question|
#application.answers.each do |answer|
#answers << answer if answer.question_id == question.id
end
end
end
private
def set_user_and_job
#user = current_user
#job = Job.find(params[:job_id])
end
def application_params
params.require(:application).permit(:job_id, :user_id, answers_attributes:[:question_id, :content]).merge(user_id: current_user.id, job_id: params[:job_id])
end
end
This is what my edit view looks like :
<% provide(:title, " Edit this application") %>
<div class="row">
<div class="span6">
<h2> Job: <%= #job.job_title %></h2>
<p> <%= #job.job_summary %> </p>
</div>
<div class="span6">
<h2> Applicant: <%= #user.name %></h2>
</div>
<div class="span12">
<h3>Edit your job application below.</h3>
</div>
</div>
<%= form_for [#job, #application] do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<% #job.questions.each_with_index do |question| %>
<%= f.fields_for :answers, question do |question_field| %>
<%= question_field.label :content, question.content %>
<%= question_field.text_area :content, :value => "" %>
<%= question_field.hidden_field :question_id, :value => question.id %>
<% end %>
<% end %>
<%= f.submit "Submit the application", class: "button" %>
<% end %>
The Application Model itself:
# == Schema Information
#
# Table name: applications
#
# id :integer not null, primary key
# user_id :integer
# job_id :integer
# created_at :datetime
# updated_at :datetime
#
class Application < ActiveRecord::Base
belongs_to :job
belongs_to :user
validates :job_id, presence: true
validates :user_id, presence: true
has_many :answers
accepts_nested_attributes_for :answers, :reject_if => lambda { |a| a[:content].blank? }, :allow_destroy => true
def self.build(job_id)
application = self.new
job = Job.find(job_id)
job.questions.count.times do
application.answers.build
end
application
end
end
And the Answer Model :
# == Schema Information
#
# Table name: answers
#
# id :integer not null, primary key
# application_id :integer
# question_id :integer
# created_at :datetime
# updated_at :datetime
# content :string(255)
#
class Answer < ActiveRecord::Base
belongs_to :question
belongs_to :application
validates :content, presence: true
end
From searching, I found this link, RoR nested attributes produces duplicates when edit , which suggests that I add the :id to application_params, however when I do that, I get the error
ActiveRecord::RecordNotFound in ApplicationsController#update
Couldn't find Answer with ID=5 for Application with ID=17
(That's also a bit weird, because the actual id of the answer is 39. 5 is actually the ID of the question :S )
What are your thoughts on this? Mentors of SO, help much appreciated :)

Answer 1

update_only does not work for has_many relationships. You need to add the nested attribute :id field to your strong parameters:
def application_params
params.require(:application).permit(:job_id, :user_id,
answers_attributes:[:id, :question_id, :content]).merge(user_id: current_user.id,
job_id: params[:job_id])
end

Answer 2

Try adding update_only to your call to accepts_nested_attributes_for.
accepts_nested_attributes_for :nested_attribute, update_only: true