Rails nested form model creation fails silently using cocoon

Question

I am using Mongoid 2.4.12 and Rails 3.2.8 with cocoon. My nested form appears to work flawlessly on the front end, but the nested model and relation are not being saved.

Project

  include Mongoid::Document
  include Mongoid::Paranoia
  include Mongoid::Timestamps

  belongs_to :user
  has_many :tasks

  accepts_nested_attributes_for :tasks, allow_destroy: true
  attr_accessible :name, :completed, :tasks_attributes

  field :name
  field :completed, type: Boolean

  validates_presence_of :name

Task

  include Mongoid::Document
  include Mongoid::Paranoia
  include Mongoid::Timestamps

  belongs_to :user
  belongs_to :category
  belongs_to :projects

  accepts_nested_attributes_for :category, allow_destroy: false
  attr_accessible :title, :description

  field :title
  field :description

Project View

<%= form_for(@project) do |f| %>
    <% if @project.errors.any? %>
        <div id="error_explanation">
            <h2><%= pluralize(@project.errors.count, "error") %> prohibited this project from being saved:</h2>
            <ul>
                <% @project.errors.full_messages.each do |msg| %>
                    <li><%= msg %></li>
                <% end %>
            </ul>
        </div>
    <% end %>
    <div class="row-fluid field-set">
        <div class="field">
            <%= f.text_field :name, placeholder: 'Name' %>
        </div>
        <div class="buttonset">
            <%= f.radio_button :completed, true, checked: true, class: 'completed-button inline' %>
            <%= label :completed, 'Completed', value: true, class: 'inline' %>
        </div>
    </div>
    <div class="row-fluid tasks-container">
        <%= link_to_add_association 'Add task', f, :tasks, class: 'btn', id: 'task-button' %>
        <%= f.fields_for :tasks do |task| %>
            <%= render 'task_fields', f: task %>
        <% end %>
    </div>
    <%= f.submit 'Save', class: 'btn', id: 'save-button' %>
<% end %>

Task Partial

<div class="new_task">
    <div class="nested-fields task-container">
        <%= link_to_remove_association 'x', f, class: 'close' %>
        <div class="field-set">
            <%= f.collection_select(:category, Category.all, :id, :name, { prompt: 'Task Type' }, { class: 'category-selector' } ) %>
        </div>
        <div class="field-set">
            <%= f.text_field :name, placeholder: 'Name', class: 'name-field' %>
        </div>
        <div class="field-set">
            <%= f.text_field :description, placeholder: 'Description', class: 'description-field' %>
        </div>
    </div>
</div>

Here are my params:

Started POST "/projects" for 127.0.0.1 at 2012-10-29 01:36:01 -0500
Processing by ProjectsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"rNX8DvKuEJgjxBvJ5c5ArTjtIMR5Uy6DtCCou0wHswk=", "project"=>{"name"=>"Example Name", "completed"=>"true", "tasks_attributes"=>{"1351491343724"=>{"_destroy"=>"", "category"=>"5089e01023499d9904000004", "title"=>"Example Title", "description"=>"Example description."}}}, "commit"=>"Save"}
MONGODB myapp_development['users'].find({:deleted_at=>nil, :_id=>BSON::ObjectId('5089a25523499d92d8000004')}).sort([[:_id, :asc]])
MONGODB myapp_development['categories'].find({:deleted_at=>nil, :_id=>BSON::ObjectId('5089e01023499d9904000004')}).sort([[:_id, :asc]])
MONGODB myapp_development['projects'].insert([{"_id"=>BSON::ObjectId('508e23d123499d2a6c00000b'), "name"=>"Example Name", "completed"=>true, "user_id"=>BSON::ObjectId('5089a25523499d92d8000004'), "updated_at"=>2012-10-29 06:36:01 UTC, "created_at"=>2012-10-29 06:36:01 UTC}])
Redirected to http://localhost:3000/projects/508e23d123499d2a6c00000b
Completed 302 Found in 24ms

As you can see, I am not getting any errors regarding accepts_nested_attributes_for, etc.

In my projects#create action, I can debug after @project.save and see that @project.tasks correctly returns an array of one task. However this task is never created/inserted/saved, and there is no relation afterward. Any suggections on what I might be missing?

Answer 1

According to the Mongoid relation docs, child elements are not automatically persisted. I am unclear on why mine are not, since accepts_nested_attributes_for should resolve this. Regardless, setting autosave: true on the relation will resolve my original problem. And for the record, cocoon will also work with has_and_belongs_to_many. Brilliant!