nested object forms

Question

I'm a rails and ruby noob, and Im pretty sure this something completely stupid I am missing..

Trying to build a nested form, and have found many examples online, and tried and failed to reproduce the desired result.

the "seller" fields are not even displayed, and when I submit form I get:

unknown attribute: item

models:

class Dealerform < ActiveRecord::Base
 belongs_to :dealer
 has_one :seller :class_name => 'Seller'
 has_many :items, :through => :seller
 accepts_nested_attributes_for :seller, :items

end

class Seller < ActiveRecord::Base
 belongs_to :dealerform
 has_many :items :class_name => 'Item'
end

class Item < ActiveRecord::Base
 belongs_to :seller
end

view:

<% form_for(@dealerform) do |f| %>
<%= f.error_messages %>
 <p>
 <%= f.label :date %><br />
 <%= f.datetime_select :date %>
 </p>
      #...more fields ...

<% f.fields_for :seller do |seller| %>

<p>
 <%= seller.label :fname %><br />
 <%= seller.text_field :fname %>
</p>
      #...more fields ...

<% end %>

 <% f.fields_for :item do |item| %>
  <p>
   <%= item.label :foo %><br />
   <%= item.text_field :foo %>
  </p>
      #...more fields ...

 <% end %>

<%= f.submit 'Create' %> 
<% end %>

Based on suggestions.. changed the following lines:

<% f.fields_for :seller do |seller| %>
<% f.fields_for :item do |item| %>

to:

<% f.fields_for @seller do |seller| %>
<% f.fields_for @item do |item| %>

and now they show up in the form, and when trying to submit form I get:

unknown attribute: nil_class

when I change:

def new
  @dealerform = Dealerform.new

to:

def new
  @dealerform = Dealerform.new
  @dealerform.seller.build

I get:

undefined method `build' for nil:NilClass

Answer 1

It's because the fields_for attribute wil only display resources that exist. In your controller you need to build objects for the forms to containe.

So in your controller

def new
    #2.times {@dealer_form.items}
    @dealer_form = DealerForm.new
    @dealer_form.seller = Seller.new
    #or @dealer_form.seller.build
end 

Answer 2

It looks like your dealerform model has_many items but your fields_for is submitting a singular item, so when it tries to initialize your dealerform in the create action it's trying to assign dealerform.item but there's no such method. If a dealerform has many items you may want to check out this example http://media.pragprog.com/titles/fr_arr/multiple_models_one_form.pdf for how to manage the has_many in a single form.

Answer 3

As Sam indicated, you ned to have an actual object, whether new or existing:

f.fields_for @seller

You can get @seller in several different ways, using build to create a new one, or if you are editing an existing record, use @dealerform.seller.

In the case of items, you may need to loop over several, depending on how many form you want to display. Check out http://www.railscasts.com for some screencasts on this.