Nested model form: one subclass isn't saving its changes

I'm working with a nested model form that appears to be working from the browser experience. When I submit the form, however, only one subclass gets updated properly.

Here are the models:

User:

class User < ActiveRecord::Base
  has_many :ducks
  has_many :places
  accepts_nested_attributes_for :ducks, :places
  ...
end

Duck:

class Duck < ActiveRecord::Base
  belongs_to :user
    attr_accessible :name, :selected
  ...
end

Place:

class Place < ActiveRecord::开发者_运维技巧Base
  belongs_to :user
    attr_accessible :name, :address
end

And the form:

<%= form_for(@user) do |user_form| %>
  <div class="field">
    <%= user_form.label :first_name %><br />
    <%= user_form.text_field :first_name %>
  </div>
  .
  .
  .
  <% user_form.fields_for :ducks do |duck_form| %>
    <%= duck_form.label duck_form.object.name %>
    <% unless duck_form.object.new_record? %>
      <%= duck_form.check_box 'selected?' %>
      <%= duck_form.label 'selected?', 'Enabled' %>
      <br />
    <% end %>
  <% end %>

  <% user_form.fields_for :places do |place_form| %>
    <%= place_form.label place_form.object.name %>
        <%= place_form.text_field :address %>
        <br />
  <% end %>

  <div class="actions">
    <%= user_form.submit "Update" %>
  </div>
<% end %>

When I submit the form, the user data (parent class) is updated, and the ducks are properly selected/deselected (child class 1) but the places (child class 2) retain their prior value.

Why are the Place fields not updating?

---

Edit: Updated question to reflect migration from alias to place, thanks to rdvdijk's comment. Unfortunately this didn't fix the problem.

---

Edit 2: Here's the relevant bit from my log file.

Started POST "/users/1" for 127.0.0.1 at 2011-09-29 14:57:27 -0700
  Processing by UsersController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"CILQ3U47rQtR9kJZ6ToAfJ7fgwqCRnrMALDZxELmFQg=", "user"=>{"first_name"=>"Foo", "last_name"=>"Man", "email"=>"foo@man.co", "password"=>"[FILTERED]", "password_confirmation"=>"[FILTERED]", "ducks_attributes"=>{"0"=>{"selected"=>"1", "id"=>"1"}, "1"=>{"selected"=>"1", "id"=>"2"}}, "places_attributes"=>{"0"=>{"address"=>"werwerwerwe", "id"=>"1"}, "1"=>{"address"=>"oiwneroinwer", "id"=>"2"}}}, "commit"=>"Update", "id"=>"1"}
  User Load (0.4ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1
  CACHE (0.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1
  CACHE (0.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1
WARNING: Can't mass-assign protected attributes: places_attributes

Clearly the last line is the problem. But even extending attr_accessible to include all of Place's fields (:name, :address, :id, :user_id, :created_at, :updated_at) doesn't solve the problem.

---

alias is a reserved keyword in Ruby. Rename your model and try again.

---

It turns out my places wasn't listed as attr-accessible, and unfortunately I hadn't included these lines in my original question:

attr_accessor :password
attr_accessible :first_name, :last_name, :email, :password, :password_confirmation,
                :ducks_attributes

Adding :places_attributes fixed the problem:

attr_accessor :password
attr_accessible :first_name, :last_name, :email, :password, :password_confirmation,
                :ducks_attributes, :places_attributes

Hope this helps someone avoid the same issue; my apologies for missing that bit in my original question.