Rails - Apr 2006 - select helper question

Hi there, I try to develop a medical application using ruby on rails.

There are many categories which can contain subcategories.

I defined the model like this:

class Category < ActiveRecord::Base
	has_and_belongs_to_many :notes
	
	
	belongs_to :parent_category, :class_name=>"Category", 
:foreign_key=>"category_id"
	has_many :sub_categories, :class_name=>"Category", 
:foreign_key=>"category_id"
	
end

And scaffolded the controller with the generator. I modified the 
_form.rhtml for creating and updated to this:

<%= error_messages_for ''category'' %>

<!--[form:category]-->


<p><label
for="category_name">Name</label><br/>
<%= text_field ''category'', ''name'' 
%></p>
<p>Abspeichern unter:<br/>
<%= select ''category'',''parent_category'',
Category.find_all.collect {|p|
[p.name,p.id]} %></p>
<!--[eoform:category]-->


I''d like that the select tag contained all categories. After I commit 
the form, I''ve got a

ActiveRecord::AssociationTypeMismatch in Admin#update

Category expected, got String

exception as the params[:category][:parent_category] contains a number, 
not a object of Category.

I have fixed this ad hoc by adding

params[:category][:parent_id] = 
Category.find(params[:category][:parent_id])

in the action methods in the controller before the


Category.new(params[:category]) or the 
@category.update_attributes(params[:category])

are called.

How can I modify the select helper to display the name of the object an 
pass the object to the params hash directly?


TIA,
-- 
Daniel V?lkerts
Protected by Anti Pesto. -- Wallace & Gromit

Daniel V?lkerts wrote:
> class Category < ActiveRecord::Base
>     has_and_belongs_to_many :notes
>     belongs_to :parent_category, :class_name=>"Category",
:foreign_key=>"category_id"
>     has_many :sub_categories, :class_name=>"Category",
:foreign_key=>"category_id"
> end
> 
> <%= select
''category'',''parent_category'',
Category.find_all.collect {|p| [p.name,p.id]} %></p>
> 
> ActiveRecord::AssociationTypeMismatch in Admin#update
> Category expected, got String
Use the foreign key in the select helper directly:

<%= select :category, :category_id, ...

-- 
We develop, watch us RoR, in numbers too big to ignore.