UnknownAttributeError using build for virtual attribute

Question

I have a nested form containing virtual attributes :card_number and :card_verification. When I try to build with these in the controller update action, I get ActiveRecord::UnknownAttributeError.

The models have a simple has_one relationship, where an appointment has_one order

#/models/appointment.rb
class Appointment < ActiveRecord::Base
  has_one :order
  accepts_nested_attributes_for :order

  attr_accessible (...)
end

#/models/order.rb
class Order < ActiveRecord::Base
  belongs_to :appointment

  attr_accessible :email, (...)
  attr_accessor :card_number, :card_verification
end

I'm generating the form like this:

# /views/appointments/edit.html.erb
<%= form_for @appointment do |f| %>
  ...
  <%= f.fields_for @appointment.order do |builder| %>
    <%= builder.label :email %>
    <%= builder.text_field :email %> # works fine on its own
    ...
    <%= f.label :card_number %>
    <%= f.text_field :card_number %>

    <%= f.label :card_verification %>
    <%= f.text_field :card_verification %>
  <% end %>
  ...
<% end %>

And building in the controller:

# /controllers/appointments_controller.rb
def update
  @appointment = Appointment.find(params[:id])
  @order = @appointment.build_order(params[:appointment]['order']) # This line is failing

  if @appointment.update_attributes(params[:appointment].except('order'))
    # ... Success
  else
    # ... Failure
  end
end

With this, I'm getting the error Can't mass-assign protected attributes: card_number, card_verification when I try to submit for update, with params:

{"utf8"=>"✓",
 "_method"=>"put",
 "authenticity_token"=>"KowchWLNmD9YtPhWhYfrNAOsDfhb7XHW5u4kdZ4MJ4=",
 "appointment"=>{"business_name"=>"Name",
 "contact_method"=>"Phone",
 "contact_id"=>"555-123-4567",
 "order"=>{"email"=>"[email protected]",
 "first_name"=>"John",
 "last_name"=>"Doe",
 "card_number"=>"4111111111111111", # normally [FILTERED]
 "card_verification"=>"123", # normally [FILTERED]
 "card_type"=>"visa",
 "card_expires_on(1i)"=>"2015",
 "card_expires_on(2i)"=>"11",
 "card_expires_on(3i)"=>"1",
 "address_line_1"=>"123 Main St",
 "address_line_2"=>"",
 "city"=>"Anywhere",
 "state"=>"CA",
 "country"=>"USA",
 "postal_code"=>"90210"}},
 "commit"=>"Submit",
 "id"=>"2"}

Everything works fine without the :card_number and :card_verification values included in the form.

Does anyone know what is going wrong here?

Edit:

I can get this working with:

@order = @appointment.build_order(params[:appointment]['order'].except('card_number', 'card_verification'))

but this seems a bit clunky. Are there any other ways to get around this?

Answer 1

The error message "Can't mass-assign protected attributes" is all about Mass Assignment Security. You can pass without_protection to ignore the mass assignment check.

@order = @appointment.build_order(params[:appointment]['order'], without_protection: true)

This link explains what is mass assignment security. Rails Internals: Mass Assignment Security

If you want to specify mass assignable attrs, use attr_accessible :one, :another for your model attributes. If you need other non-model attributes, use attr_accessor :card_number, and then attr_accessible :card_number to declare and expose it.

I see you define card_number and card_verfication in Order model, but you use form_builder => f to define these two fields in html. Try using fields_for builder instead.