#5337 accepts_nested_attributes_for bug? - Ruby on Rails

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#5337 ✓invalid

accepts_nested_attributes_for bug?

Reported by Matt Simpson | August 9th, 2010 @ 05:59 AM

I have a new model object
with accepts_nested_attributes_for to an associated model
When I go to the html form, the fields for those nested attributes are not rendered

But, if I have a model object where that associated model object is saved, the form is rendered with the correct data.

Is there anything I need to do to get the form fields for the nested attributes render when no data exists? Or is this method only for associated objects already created?

I've attached screenshots. 1 has data and renders the form, the other does not.

Models:

class Booking < ActiveRecord::Base
  has_one :event_address, :as => :addressee

  accepts_nested_attributes_for :event_address
end

class EventAddress < ActiveRecord::Base
  belongs_to :addressee, :polymorphic => true
end

Haml:

= form_for @booking, :url => booking_event_information_path(@booking) do |f|
  = f.error_messages
  
  = f.fields_for :event_address do |f2| 
    = f2.label :address_1, "Address"
    = f2.text_field :address_1
    %br
  
    = f2.label :address_2
    = f2.text_field :address_2
    %br
  
  = f.submit "Save event information"

Any help is much helpful :) Thanks.

screen-shot-2010-08-08-at-115556-pm.png 45.3 KB
screen-shot-2010-08-08-at-115608-pm.png 41.5 KB

Comments and changes to this ticket

You flagged this item as spam.
kylc August 9th, 2010 @ 09:03 PM
Make sure that you're building the nested model in the controller before rendering the form:
```
def new
  @booking = Booking.new
  @booking.addressee.build
end
```
You flagged this item as spam.
Matt Simpson August 10th, 2010 @ 04:38 AM
- Tag changed from “active record, activerecord associations, nested attributes, activerecord” to “active record, activerecord associations, nested attributes, rails 3.0.0.beta4, activerecord”
I'm terribly sorry, I forgot to mention this is in Rails 3:
```
[msimpson@dakota Code] (master) $ ruby -v
ruby 1.9.2dev (2010-07-02 revision 28524) [x86_64-darwin10.4.0]
[msimpson@dakota Code] (master) $ rails -v
Rails 3.0.0.beta4
```
When I call the build method on the end of either @booking.event_address or @booking.addressee I get:
```
NoMethodError (undefined method `build' for nil:NilClass):
  app/controllers/booking_controller.rb:17:in `event_information'
```
Thanks
You flagged this item as spam.
Matt Simpson August 10th, 2010 @ 04:43 AM
However, looking further into the documentation (note that build is not in the method list) the correct usage is:

@booking.build_event_information and doing so does render the form. Thank you, is this by design for the accepts_nested_attributes_for method? If I do not have accepts_nested_attributes_for set the fields do render, just not with the functionality needed. Perhaps this should be in the documentation for accepts_nested_attributes_for?

Thank you for your help and direction.
Rohit Arondekar October 7th, 2010 @ 05:21 AM
- Tag changed from “active record, activerecord associations, nested attributes, rails 3.0.0.beta4, activerecord” to “active record, nested attributes, rails 3.0.0.beta4, activerecord, associations”
[bulk edit]
Aditya Sanghi October 7th, 2010 @ 08:48 AM
@matt, just chiming in here as a fellow user.

Yes this is the intended functionality. When you are using accepts_nested_attributes_for, the association needs to be built before the form can be rendered. The method used for building does depend on the type of association you have (has_many or belongs_to etc) in the base model and is not really connected to the attribute_nested_for issue.

If you do not use accepts_nested_attributes_for, the keys in received from the form params in your model differ to when you do use accepts_nested_attributes_for in your base model differ and you have to manually write the plumbing in your model (or elsewhere) to ensure the association is built and saved.

Ryan has a set of Railscasts on Complex forms which explain the functionality very well. I think there is a Rails Guide on Nested form in progress which when released would serve as authoritative documentation on the feature.
David Trasbo October 7th, 2010 @ 08:56 PM
- State changed from “new” to “invalid”
- Importance changed from “” to “Low”
fields_for not rendering anything if no object(s) are built is the intended behavior.