Getting fields_for and accepts_nested_attributes_for to work with a belongs_to relationship
- by Billy Gray
I cannot seem to get a nested form to generate in a rails view for a belongs_to relationship using the new accepts_nested_attributes_for facility of Rails 2.3. I did check out many of the resources available and it looks like my code should be working, but fields_for explodes on me, and I suspect that it has something to do with how I have the nested models configured.
The error I hit is a common one that can have many causes:
'@account[owner]' is not allowed as an instance variable name
Here are the two models involved:
class Account < ActiveRecord::Base
# Relationships
belongs_to :owner, :class_name => 'User', :foreign_key => 'owner_id'
accepts_nested_attributes_for :owner
has_many :users
end
class User < ActiveRecord::Base
belongs_to :account
end
Perhaps this is where I am doing it 'rong', as an Account can have an 'owner', and may 'users', but a user only has one 'account', based on the user model account_id key.
This is the view code in new.html.haml that blows up on me:
- form_for :account, :url => account_path do |account|
= account.text_field :name
- account.fields_for :owner do |owner|
= owner.text_field :name
And this is the controller code for the new action:
class AccountsController < ApplicationController
# GET /account/new
def new
@account = Account.new
end
end
When I try to load /account/new I get the following exception:
NameError in Accounts#new
Showing app/views/accounts/new.html.haml where line #63 raised:
@account[owner] is not allowed as an instance variable name
If I try to use the mysterious 'build' method, it just bombs out in the controller, perhaps because build is just for multi-record relationships:
class AccountsController < ApplicationController
# GET /account/new
def new
@account = Account.new
@account.owner.build
end
end
You have a nil object when you didn't expect it!
The error occurred while evaluating nil.build
If I try to set this up using @account.owner_attributes = {} in the controller, or @account.owner = User.new, I'm back to the original error, "@account[owner] is not allowed as an instance variable name".
Does anybody else have the new accepts_nested_attributes_for method working with a belongs_to relationship? Is there something special or different you have to do? All the official examples and sample code (like the great stuff over at Ryans Scraps) is concerned with multi-record associations.
