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-**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
-
-Rails Nested Model Forms
-========================
-
-Creating a form for a model _and_ its associations can become quite tedious. Therefore Rails provides helpers to assist in dealing with the complexities of generating these forms _and_ the required CRUD operations to create, update, and destroy associations.
-
-After reading this guide, you will know:
-
-* do stuff.
-
---------------------------------------------------------------------------------
-
-NOTE: This guide assumes the user knows how to use the [Rails form helpers](form_helpers.html) in general. Also, it's **not** an API reference. For a complete reference please visit [the Rails API documentation](http://api.rubyonrails.org/).
-
-
-Model setup
------------
-
-To be able to use the nested model functionality in your forms, the model will need to support some basic operations.
-
-First of all, it needs to define a writer method for the attribute that corresponds to the association you are building a nested model form for. The `fields_for` form helper will look for this method to decide whether or not a nested model form should be built.
-
-If the associated object is an array, a form builder will be yielded for each object, else only a single form builder will be yielded.
-
-Consider a Person model with an associated Address. When asked to yield a nested FormBuilder for the `:address` attribute, the `fields_for` form helper will look for a method on the Person instance named `address_attributes=`.
-
-### ActiveRecord::Base model
-
-For an ActiveRecord::Base model and association this writer method is commonly defined with the `accepts_nested_attributes_for` class method:
-
-#### has_one
-
-```ruby
-class Person < ApplicationRecord
-  has_one :address
-  accepts_nested_attributes_for :address
-end
-```
-
-#### belongs_to
-
-```ruby
-class Person < ApplicationRecord
-  belongs_to :firm
-  accepts_nested_attributes_for :firm
-end
-```
-
-#### has_many / has_and_belongs_to_many
-
-```ruby
-class Person < ApplicationRecord
-  has_many :projects
-  accepts_nested_attributes_for :projects
-end
-```
-
-NOTE: For greater detail on associations see [Active Record Associations](association_basics.html).
-For a complete reference on associations please visit the API documentation for [ActiveRecord::Associations::ClassMethods](http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html).
-
-### Custom model
-
-As you might have inflected from this explanation, you _don't_ necessarily need an ActiveRecord::Base model to use this functionality. The following examples are sufficient to enable the nested model form behavior:
-
-#### Single associated object
-
-```ruby
-class Person
-  def address
-    Address.new
-  end
-
-  def address_attributes=(attributes)
-    # ...
-  end
-end
-```
-
-#### Association collection
-
-```ruby
-class Person
-  def projects
-    [Project.new, Project.new]
-  end
-
-  def projects_attributes=(attributes)
-    # ...
-  end
-end
-```
-
-NOTE: See (TODO) in the advanced section for more information on how to deal with the CRUD operations in your custom model.
-
-Views
------
-
-### Controller code
-
-A nested model form will _only_ be built if the associated object(s) exist. This means that for a new model instance you would probably want to build the associated object(s) first.
-
-Consider the following typical RESTful controller which will prepare a new Person instance and its `address` and `projects` associations before rendering the `new` template:
-
-```ruby
-class PeopleController < ApplicationController
-  def new
-    @person = Person.new
-    @person.build_address
-    2.times { @person.projects.build }
-  end
-
-  def create
-    @person = Person.new(params[:person])
-    if @person.save
-      # ...
-    end
-  end
-end
-```
-
-NOTE: Obviously the instantiation of the associated object(s) can become tedious and not DRY, so you might want to move that into the model itself. ActiveRecord::Base provides an `after_initialize` callback which is a good way to refactor this.
-
-### Form code
-
-Now that you have a model instance, with the appropriate methods and associated object(s), you can start building the nested model form.
-
-#### Standard form
-
-Start out with a regular RESTful form:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-<% end %>
-```
-
-This will generate the following html:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-</form>
-```
-
-#### Nested form for a single associated object
-
-Now add a nested form for the `address` association:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-
-  <%= f.fields_for :address do |af| %>
-    <%= af.text_field :street %>
-  <% end %>
-<% end %>
-```
-
-This generates:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-
-  <input id="person_address_attributes_street" name="person[address_attributes][street]" type="text" />
-</form>
-```
-
-Notice that `fields_for` recognized the `address` as an association for which a nested model form should be built by the way it has namespaced the `name` attribute.
-
-When this form is posted the Rails parameter parser will construct a hash like the following:
-
-```ruby
-{
-  "person" => {
-    "name" => "Eloy Duran",
-    "address_attributes" => {
-      "street" => "Nieuwe Prinsengracht"
-    }
-  }
-}
-```
-
-That's it. The controller will simply pass this hash on to the model from the `create` action. The model will then handle building the `address` association for you and automatically save it when the parent (`person`) is saved.
-
-#### Nested form for a collection of associated objects
-
-The form code for an association collection is pretty similar to that of a single associated object:
-
-```erb
-<%= form_for @person do |f| %>
-  <%= f.text_field :name %>
-
-  <%= f.fields_for :projects do |pf| %>
-    <%= pf.text_field :name %>
-  <% end %>
-<% end %>
-```
-
-Which generates:
-
-```html
-<form action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-
-  <input id="person_projects_attributes_0_name" name="person[projects_attributes][0][name]" type="text" />
-  <input id="person_projects_attributes_1_name" name="person[projects_attributes][1][name]" type="text" />
-</form>
-```
-
-As you can see it has generated 2 `project name` inputs, one for each new `project` that was built in the controller's `new` action. Only this time the `name` attribute of the input contains a digit as an extra namespace. This will be parsed by the Rails parameter parser as:
-
-```ruby
-{
-  "person" => {
-    "name" => "Eloy Duran",
-    "projects_attributes" => {
-      "0" => { "name" => "Project 1" },
-      "1" => { "name" => "Project 2" }
-    }
-  }
-}
-```
-
-You can basically see the `projects_attributes` hash as an array of attribute hashes, one for each model instance.
-
-NOTE: The reason that `fields_for` constructed a hash instead of an array is that it won't work for any form nested deeper than one level deep.
-
-TIP: You _can_ however pass an array to the writer method generated by `accepts_nested_attributes_for` if you're using plain Ruby or some other API access. See (TODO) for more info and example.