Rails 3 fields_for wont assocoiate

Question

In my Rails 3 App, my fields for won't associate, I've been researching and I can't figure out why.

My view:

 = form_for(resource, class: 'admin_form', :as => resource_name, :url => registration_path(resource_name))  do |f|
    = devise_error_messages!
    .admin_form
      ...

      = fields_for :profile do |p|
        ...
        %dl
          %dd
            = f.submit "Sign up", class: "btn"

Controller:

class RegistrationsController < Devise::RegistrationsController
  before_filter :check_admin_quantity

  def new
    super
  @profile = @user.build_profile
end

Model:

class User < ActiveRecord::Base
attr_accessible :email, :password, :password_confirmation, :remember_me,     :current_password, :profile_attributes
has_one :profile, dependent: :destroy
accepts_nested_attributes_for :profile

Answer 1

Firstly use f.fields_for instead of fields_for. The later only creates the fields, but they are not associated with a form object, former is creating fields for associated object.

When you add f. you will notice that it is not rendering fields. It is caused by your resource not having associated profile. You are building profile on @user, but it is different than resource object.

If you have a look at default implementation of new, it reads:

def new
  build_resource({})
  respond_with self.resource
end

you are calling this calling super in your new method. You need to build profile between build_resource and respond_with, so your new action should be:

def new
  build_resource({})
  resource.build_profile
  respond_with self.resource
end