Getting fields_for and accepts_nested_attributes_for to work with a belongs_to relationship

I'm a few months too late, but I was looking to solve this error and my situation was that I could not change the relationship to 'face the other way'.

The answer really is quite simple, you have to do this in your new action:

@account.build_owner

The reason why the form did not display using fields_for was because it did not have a valid object. You had the right idea up there with:

@account.owner.build

However, this is not the way belongs_to work. This method is only generated with has_many and has_and_belongs_to_many.

Reference:http://guides.rubyonrails.org/association_basics.html#belongs-to-association-reference

I'm using Rails 2.3.5 and I noticed the same thing. Checking out the source for active_record's nested_attributes.rb, it looks like belongs_to should work fine. So it appears it might be a "nested forms" bug.

I have a nested form exactly like yours, with User belongs_to :address, and Address is independent of the user.

Then in the form, I just do <% f.fields_for :address_attributes do |address_form| %> instead of <% f.fields_for :address do |address_form| %>. Temporary hack until there's a better way, but this works. The method accepts_nested_attributes_for is expecting the params to include something like:

{user=>{address_attributes=>{attr1=>'one',attr2=>'two'}, name=>'myname'}

...but fields_for is producing:

{user=>{address=>{attr1=>'one',attr2=>'two'}, name=>'myname'}

This way you don't have to add that has_one :account to your code, which doesn't work in my case.

Update: Found a better answer:

Here is the gist of the code I'm using to make this work right:

Rails Nested Forms with belongs_to Gist

Hope that helps.

I think your accepts_nested_attributes is on the wrong side of the relationship. Maybe something like this would work?

class Account < ActiveRecord::Base  belongs_to :owner, :class_name => 'User', :foreign_key => 'owner_id'  has_many :usersendclass User < ActiveRecord::Base  belongs_to :account  has_one :account, :foreign_key => :owner_id  accepts_nested_attributes_for :accountend

For building the account you want to use build_account.

You can see more examples in the docs.