title: Nested Resource ActiveAdmin
body: <p>I am using ActiveAdmin and attempting to do a very simple nested form. I have reviewed a lot of answers to similar questions that don't work. </p>
  
  <p>Below I've created a form that only includes one field called dba_number of the business model.</p>
  
  <p>I get the following error when I attempt to save a new Address</p>
  
  <p>Can't mass-assign protected attributes: business</p>
  
  <p>I've read a lot about this security feature and even reviewed Ryan Bates's nested form tutorial. I can't see anything else to change with this. </p>
  
  <p>Can anyone explain to me what I'm missing?</p>
  
  <p>Here is my code</p>
  
  <pre><code>#app/models/business.rb
  
  class Business &lt; ActiveRecord::Base
    attr_accessible :dba_number, :name, :industry_id, :address_id
    has_and_belongs_to_many :owners
    belongs_to :industry
    belongs_to :address
    end
  end
  
  #app/models/address.rb
  
  class Address &lt; ActiveRecord::Base
    attr_accessible :street_number, :post_office_box_number, :apartment_number, :street_name, :street_suffix_id, :city, :zip_code, :state_id, :businesses_attributes, :permits_attributes
    validates_presence_of :city, :zip_code
    has_many :owners
    has_many :businesses
    has_many :permits
    belongs_to :street_suffix
    belongs_to :state
  end
  
  #admin/addresses.rb file
  
  ActiveAdmin.register Address do
  
    form :partial =&gt; 'form'
  
    controller do
      def new
        new! do |format|
          @address = Address.new
        end
      end
  
      def create
        create! do |format|
          address = Menu.find(params[:address])
          if @address.save
            redirect_to {admin_address_url}
          end
        end
      end
    end
  
  end
  
  app/views/admin/addresses/_form.html.erb
  
  &lt;%= semantic_nested_form_for [:admin, @address] do |f| %&gt;
      &lt;%= f.inputs "Details" do %&gt;
        &lt;%= f.input :street_number %&gt;
        &lt;%= f.input :post_office_box_number %&gt;
        &lt;%= f.input :apartment_number %&gt;
        &lt;%= f.input :street_name %&gt;
        &lt;%= f.input :street_suffix , :as =&gt; :select, :collection =&gt; Hash[StreetSuffix.all.map{|a| [a.suffix_name, a.id]}] %&gt;
        &lt;%= f.input :state, :as =&gt; :select, :collection =&gt; Hash[State.all.map{|s| [s.abbr, s.id]}] %&gt;
        &lt;%= f.input :city %&gt;
        &lt;%= f.input :zip_code %&gt;
        &lt;%= f.inputs :dba_number, :for =&gt; :business, :name =&gt; "Business" %&gt;
  
  &lt;% end %&gt;
      &lt;%= f.actions %&gt;
  </code></pre>