rails devise: user and account system - ruby-on-rails

Question

I've been trying to add an account to a user for a couple of days now.
I've installed Devise with no problems, but now I wanted to add a Company Name field to my registration form.
Here's my code:
app/models/account.rb
class Account < ActiveRecord::Base
attr_accessible :name
has_many :users
accepts_nested_attributes_for :users
end
app/models/user.rb
class User < ActiveRecord::Base
belongs_to :account
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable, :confirmable
attr_accessible :first_name, :last_name, :account_attributes, :account, :email, :password, :password_confirmation, :remember_me
end
app/views/devise/registrations/new.html.erb
<%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %>
<%= devise_error_messages! %>
<div><%= f.label :first_name %><br />
<%= f.text_field :first_name %></div>
<div><%= f.label :last_name %><br />
<%= f.text_field :last_name %></div>
<%= f.fields_for :account do |account_form| %>
<div><%= account_form.label :name %><br />
<%= account_form.text_field :name %></div>
<% end %>
<div><%= f.label :email %><br />
<%= f.email_field :email %></div>
<div><%= f.label :password %><br />
<%= f.password_field :password %></div>
<div><%= f.label :password_confirmation %><br />
<%= f.password_field :password_confirmation %></div>
<div><%= f.submit "Sign up" %></div>
<% end %>
This is all the code I have. I haven't changed anything more.
And this is the error I got:
Account(#2175324980) expected, got ActiveSupport::HashWithIndifferentAccess(#2169631580)
Thanks in advance.
EDIT
I've found the solution:
I've changed
<%= f.fields_for :account do |account_form| %>
To
<%= f.fields_for :account_attributes, resource.account do |account_form| %>
Now I'm trying to add a :plan to account_form and I'm getting:
Can't mass-assign protected attributes: plan
EDIT 2
Ok, rookie mistake. I've just added :plan to account model.
After that I was getting an query error, I just changed some fields in my DB from null => false to null => true and voila.

Answer 1

I would expect it to look something like this. This involves subclassing devise's registrations controller
#models
class Account < ActiveRecord::Base
attr_accessible :name
has_many :users
end
class User < ActiveRecord::Base
belongs_to :account
accepts_nested_attributes_for :account
attr_accessible :first_name, :last_name, :account_attributes, :account, :email, :password, :password_confirmation, :remember_me
end
#app/controllers/registrations_controller.rb
class RegistrationsController < Devise::RegistrationsController
def new
#account = Account.new
super
end
end
#routes
devise_for :users, :controllers => {:registrations => "registrations"}
#view
<%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %>
<%= devise_error_messages! %>
<div><%= f.label :first_name %><br />
<%= f.text_field :first_name %></div>
<div><%= f.label :last_name %><br />
<%= f.text_field :last_name %></div>
<%= f.fields_for #account do |account_form| %>
<div><%= account_form.label :name %><br />
<%= account_form.text_field :name %></div>
<% end %>
<div><%= f.label :email %><br />
<%= f.email_field :email %></div>
<div><%= f.label :password %><br />
<%= f.password_field :password %></div>
<div><%= f.label :password_confirmation %><br />
<%= f.password_field :password_confirmation %></div>
<div><%= f.submit "Sign up" %></div>
<% end %>