Nested forms with multiple table inheritance - ruby-on-rails

Question

How do I build a nested form for objects using multiple table inheritance in rails? I am trying to make a nested form to create an object using a model with a has_many relationship to another set of models that feature multi-table inheritance. I am using formtastic and cocoon for the nested form and the act_as_relation gem to implement the multiple table inheritance.
I have the following models:
class Product < ActiveRecord::Base
acts_as_superclass
belongs_to :store
end
class Book < ActiveRecord::Base
acts_as :product, :as => :producible
end
class Pen < ActiveRecord::Base
acts_as :product, :as => :producible acts_as :product, :as => :producible
end
class Store < ActiveRecord::Base
has_many :products
accepts_nested_attributes_for :products, :allow_destroy => true, :reject_if => :all_blank
end'
For this example, the only unique attribute that book has compared to other products is an author field. In reality, I have a number of unique attributes for book which is why I chose multi-table inheritance over the more commonplace single table inheritance.
I am trying to create a nested form that allows you to create a new store with products. Here's my form:
<%= semantic_form_for #store do |f| %>
<%= f.inputs do %>
<%= f.input :name %>
<h3>Books/h3>
<div id='books'>
<%= f.semantic_fields_for :books do |book| %>
<%= render 'book_fields', :f => book %>
<% end %>
<div class='links'>
<%= link_to_add_association 'add book', f, :books %>
</div>
<% end %>
<%= f.actions :submit %>
<% end %>
And the book_fields partial:
<div class='nested-fields'>
<%= f.inputs do %>
<%= f.input :author %>
<%= link_to_remove_association "remove book", f %>
<% end %>
</div>
I get this error:
undefined method `new_record?' for nil:NilClass
Based on reading the issues on the github page for act_as_relation, I thought about making the relationship between store and books more explicit:
class Product < ActiveRecord::Base
acts_as_superclass
belongs_to :store
has_one :book
accepts_nested_attributes_for :book, :allow_destroy => true, :reject_if => :all_blank
end
class Book < ActiveRecord::Base
belongs_to :store
acts_as :product, :as => :producible
end
class Store < ActiveRecord::Base
has_many :products
has_many :books, :through => :products
accepts_nested_attributes_for :products, :allow_destroy => true, :reject_if => :all_blank
accepts_nested_attributes_for :books, :allow_destroy => true, :reject_if => :all_blank
end
Now, I get a silent error. I can create new stores using the form, and cocoon allows me to add new book fields, but when I submit the store gets created but not the child book. When, I go through the `/books/new' route, I can create a new book record that spans (the products and books table) with no problem.
Is there a workaround to this problem? The rest of the code can be found here.

Answer 1

Maybe you could:
Build the books relation manually on your stores_controller#new action
#store.books.build
Store manually the relation on you stores_controller#create action
#store.books ... (not really confident on how to achieve it)
Keep us posted.

Answer 2

You might want to consider creating your own form object. This is a RailsCast pro video, but here are some of the examples in the ASCIIcast:
def new
#signup_form = SignupForm.new(current_user)
end
This signup form can include relations to your other objects, just as you would in your original controller code:
class SignupForm
# Rails 4: include ActiveModel::Model
extend ActiveModel::Naming
include ActiveModel::Conversion
include ActiveModel::Validations
validates_presence_of :username
validates_uniqueness_of :username
validates_format_of :email, with: /\A([^#\s]+)#((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/
validates_length_of :password, minimum: 6
def persisted?
false
end
def subscribed
subscribed_at
end
def subscribed=(checkbox)
subscribed_at = Time.zone.now if checkbox == "1"
end
def generate_token
begin
self.token = SecureRandom.hex
end while User.exists?(token: token)
end
end
Here is the link to the RailsCast. Getting a pro membership might be worth your time. I have been getting lucky with a membership through www.codeschool.com where you can get 'prizes' when you finish courses:
RailsCast:
http://railscasts.com/episodes/416-form-objects