Rails Polymorphic Association，在尝试创建new时，从form_for导致'nil不是符号'TypeError

Question

User Model

belongs_to :role, :polymorphic => true

admin_profile model (NOT ACTUAL NAME, BUT YOU GET THE IDEA)

has_one :user, :as => :role

user_profile model (NOT ACTUAL NAME, BUT YOU GET THE IDEA. There are others beyond these two.)

has_one :user, :as => :role

When I visit /admin_profile/new, I get 'nil is not a symbol' TypeError on line #1.

<%= form_for(@admin_profile) do |f| %>
    ...

The contents of @admin_profile are:

<AdminProfile id: nil, birth_date: nil, url: nil>

The trace goes like this

activerecord (3.1.1) lib/active_record/attribute_methods/primary_key.rb:8:in `to_key'
actionpack (3.1.1) lib/action_controller/record_identifier.rb:76:in `record_key_for_dom_id'
actionpack (3.1.1) lib/action_controller/record_identifier.rb:57:in `dom_id'
actionpack (3.1.1) lib/action_view/helpers/form_helper.rb:388:in `apply_form_for_options!'
actionpack (3.1.1) lib/action_view/helpers/form_helper.rb:365:in `form_for'

If there is any other information required, let me know.

Answer 1

The problem was some of the tables had :id => false. Let this be a warning to would be users of db:schema:dump