Rails - Nov 2010 - Creating an association with accepts_nested_attributes_for

I have 2 models, Category and LineItemTypes

There are already plenty existing of both, it is now a requirement for
them to be associated. Being many LineItemTypes for every Category.

I have added accepts_nested_attributes_for :line_item_types on Category

I''ve tried using a hidden_field on a form to create a list of existing
associated LineItemTypes:

- form_for @category do |form|
  %ul#categorised
    - form.fields_for :line_item_types do |line_item_types|
      -categorised.each do |l|
        %li
          =l.description
          =line_item_types.hidden_field :category_id

  =form.submit

If I add an item to that list, I get errors saying that a LineItemType
for that Category can''t be found. I thought
accepts_nested_attributes_for would add the association if it doesn''t
exist. Or is it only for ''creating'' new records and modifying
existing
relationships, not creating new relationships.

a.update_attributes({:line_item_types_attributes => [{:id => 2767}, {:id
=> LineItemType.find(2).id}]})
ActiveRecord::RecordNotFound: Couldn''t find LineItemType with ID=2 for
Category with ID=1

Any ideas without having to write something to traverse the resulting
form params and create the associations? Or an even easier way to
achieving this? I have an existing association with

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Probably a silly question. Have you declared the belongs_to and
has_many associations?

On Nov 2, 11:08 am, Stuart Corbishley
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> I have 2 models, Category and LineItemTypes
>
> There are already plenty existing of both, it is now a requirement for
> them to be associated. Being many LineItemTypes for every Category.
>
> I have added accepts_nested_attributes_for :line_item_types on Category
>
> I''ve tried using a hidden_field on a form to create a list of
existing
> associated LineItemTypes:
>
> - form_for @category do |form|
>   %ul#categorised
>     - form.fields_for :line_item_types do |line_item_types|
>       -categorised.each do |l|
>         %li
>           =l.description
>           =line_item_types.hidden_field :category_id
>
>   =form.submit
>
> If I add an item to that list, I get errors saying that a LineItemType
> for that Category can''t be found. I thought
> accepts_nested_attributes_for would add the association if it
doesn''t
> exist. Or is it only for ''creating'' new records and
modifying existing
> relationships, not creating new relationships.
>
> a.update_attributes({:line_item_types_attributes => [{:id => 2767},
{:id
> => LineItemType.find(2).id}]})
> ActiveRecord::RecordNotFound: Couldn''t find LineItemType with ID=2
for
> Category with ID=1
>
> Any ideas without having to write something to traverse the resulting
> form params and create the associations? Or an even easier way to
> achieving this? I have an existing association with
>
> --
> Posted viahttp://www.ruby-forum.com/.
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Hehe not a silly question, yes, I have, I also got a recommendation to 
try using the :inverse_of argument on the relationships too. Which 
didn''t haven any effect on the problem.

I''ve come to the conclusion that accepts_nested_attributes_for works 
kinda like url_for... Where the presence of ID makes it assume the 
relationship exists. Rendering accepts_nested_attributes_for not 
suitable for what I want to do.

I''ve worked around this with a before filter:

def find_line_item_types
    params[:category][:line_item_types] = 
LineItemType.find(params[:category][:line_item_types].collect { |a| 
a[0].to_i }) if params[:category] and 
params[:category][:line_item_types]
  end

Thanks for replying! :)

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