saving to two different models - accepts_nested_attributes_for not working

Question

EDITED: code below reflects last suggestions from your answers...

I'm having trouble with saving to two different models, from one form... I tried to follow rails casts #196 and looked at several other examples here at stackoverflow but I haven't figured out how to do this because my case is a little bit different...

So, I have two models:

class Patient < ActiveRecord::Base
  attr_accessible :date_of_birth, :patient_name

  has_many :samples
end

class Sample < ActiveRecord::Base
  attr_accessible :approved, :patientID, :result, patient_attributes: [:patient_name, :date_of_birth]

  belongs_to :patient
  accepts_nested_attributes_for :patient
end

What I found on most of the examples I saw, including the railscasts, is to create a new sample inside the patient form, and the "accepts_nestes_attributes_for" is inside the "patient" model... But what I want to do is exactly the opposite, that is, creating a new patient inside the new sample form.

Here're my views, I have a normal form for the sample and then a partial for the patient part:

_form.html.erb

<%= form_for(@sample) do |f| %>
  <% if @sample.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@sample.errors.count, "error") %> prohibited this sample from being saved:</h2>

      <ul>
      <% @sample.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :result %><br />
    <%= f.text_area :result %>
  </div>
  <div class="field">
    <%= f.label :approved %><br />
    <%= f.check_box :approved %>
  </div>
  <div><%= render 'patient', f: f %></div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

patient.html.erb

<%= f.fields_for :patient do |p| %>
<div class="field">
    <%= p.label :patient_name %><br />
    <%= p.text_field :patient_name %>
</div>
<div class="field">
    <%= p.label :date_of_birth %><br />
    <%= p.date_select :date_of_birth %>
</div>
<% end %>

When I click the submit button everything seems to work, but nothing is saved into the patients table.

Here's the log:

Started POST "/samples" for 127.0.0.1 at 2013-10-12 23:32:03 +0100
Processing by SamplesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"13OKZ8DaGJ4zTb35q+ymSzx7r+Ipxou1u+XrR4jtyeI=", "sample"=>{"result"=>"teste 3", "approved"=>"0"}, "patient"=>{"patient_name"=>"Joao", "date_of_birth(1i)"=>"2013", "date_of_birth(2i)"=>"10", "date_of_birth(3i)"=>"10"}, "commit"=>"Create Sample"}
   (0.1ms)  begin transaction
  SQL (0.5ms)  INSERT INTO "samples" ("approved", "created_at", "patientID", "result", "updated_at") VALUES (?, ?, ?, ?, ?)  [["approved", false], ["created_at", Sat, 12 Oct 2013 22:32:03 UTC +00:00], ["patientID", nil], ["result", "teste 3"], ["updated_at", Sat, 12 Oct 2013 22:32:03 UTC +00:00]]
   (2.4ms)  commit transaction
Redirected to http://localhost:3000/samples/3
Completed 302 Found in 6ms (ActiveRecord: 2.9ms)

As you can see in the log, it's only saving to the sample table. Can I use accepts_nested_attributes_for this way? Is there a way to achieve what I want? Or should I try a different approach?

UPDATE: Here's the code for my patient and sample controllers:

patients_controller.rb

def new
    @patient = Patient.new

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @patient }
    end
end

def create
    @patient = Patient.new(params[:patient])

    respond_to do |format|
      if @patient.save
        format.html { redirect_to @patient, notice: 'Patient was successfully created.' }
        format.json { render json: @patient, status: :created, location: @patient }
      else
        format.html { render action: "new" }
        format.json { render json: @patient.errors, status: :unprocessable_entity }
      end
    end
end

samples_controller.rb

def new
    @sample = Sample.new
    @sample.build_patient #suggested by El Key

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @sample }
    end
end

def create
    @sample = Sample.new(params[:sample])

    respond_to do |format|
      if @sample.save
        format.html { redirect_to @sample, notice: 'Sample was successfully created.' }
        format.json { render json: @sample, status: :created, location: @sample }
      else
        format.html { render action: "new" }
        format.json { render json: @sample.errors, status: :unprocessable_entity }
      end
    end
end

Here's the updated log after I follow El Key suggestions:

Started POST "/samples" for 127.0.0.1 at 2013-10-17 00:20:05 +0100
Processing by SamplesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"NZXQUdd8tQc206LdEuYF5iO5+89wlfza0VbbvgBGNuI=", "sample"=>{"result"=>"teste 9", "patientID"=>"", "approved"=>"0", "patient_attributes"=>{"patient_name"=>"Sergio", "date_of_birth(1i)"=>"2013", "date_of_birth(2i)"=>"10", "date_of_birth(3i)"=>"2"}}, "commit"=>"Create Sample"}
Completed 500 Internal Server Error in 1ms

ActiveModel::MassAssignmentSecurity::Error - Can't mass-assign protected attributes: patient_attributes:

As you can see, now I have a problem for "can't mass-assign protected attributes", but shouldn't this work as I have the "patient_attributes" on the sample model?

After I solve this I will try to check first if the patient exists or not before committing and try to do as SAYT on the patient's name... but that's a future step!

Thanks for your help

After following El-Key advise and suggestions, I found the solution

Update, Final Code - My solution

models/samples.rb

class Sample < ActiveRecord::Base
  attr_accessible :approved, :patient_id, :result, :patient_attributes

  belongs_to :patient
  accepts_nested_attributes_for :patient
end

models/patient.rb

class Patient < ActiveRecord::Base
  attr_accessible :date_of_birth, :patient_name 
  has_many :samples
end

controllers/samples_controller

def new
    @sample = Sample.new
    @sample.build_patient

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @sample }
    end
end

def create
    @sample = Sample.new(params[:sample])

    respond_to do |format|
      if @sample.save
        format.html { redirect_to @sample, notice: 'Sample was successfully created.' }
        format.json { render json: @sample, status: :created, location: @sample }
      else
        format.html { render action: "new" }
        format.json { render json: @sample.errors, status: :unprocessable_entity }
      end
    end
end

views/samples/_form.html.erb

<%= form_for(@sample) do |f| %>
  <% if @sample.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@sample.errors.count, "error") %> prohibited this sample from being saved:</h2>

      <ul>
      <% @sample.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :result %><br />
    <%= f.text_area :result %>
  </div>
    <div class="field">
        <%= f.label :patient_id, 'Patient ID' %><br />
        <%= f.text_area :patient_id %>
    </div>
  <div class="field">
    <%= f.label :approved %><br />
    <%= f.check_box :approved %>
  </div>

  <div><%= render 'patient', f: f %></div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

views/samples/_patient.html.erb

<%= f.fields_for :patient do |p| %>
<div class="field">
       <%= p.label :patient_name %><br />
       <%= p.text_field :patient_name %>
</div>
<div class="field">
       <%= p.label :date_of_birth %><br />
       <%= p.date_select :date_of_birth %>
</div>
<% end %>

Answer 1

The fields_for method has to be call from the parent form, such as :

_form.html.erb

<div><%= render 'patient', f: f %></div>

patient.html.erb

<%= f.fields_for :patient do |p| %>
  <!-- code -->
<% end %>

Try this. If it's still not working, could you please show us your controller. Hope this help

EDIT
Ok then try to replace in your Sample model patient by patient_attributes as :

attr_accessible patient_attributes: [:patient_name, :date_of_birth]

Answer 2

1. If you have patientID which is a different field and not the foreign key in samples table, you have to make it available via , :patient_id or leave it if patientID is meant for a different purpose.

2. you need to give an new object for the fields for

Change your sample model like this

attr_accessible :approved, :patientID, :result, :patient_attributes

And sample form line from

<div><%= render 'patient', f: f %></div>

to

<div>
<%= f.fields_for :patient, Patient.new do |p| %>
  <%= p.text_field :name %>
  <%= p.text_field :date_of_birth %>
<% end %>
</div>

I've created a sample app for you to understand how it works.

https://github.com/ravensnowbird/inverse_nested

You can remove @sample.build_patient as well.