ActiveScaffold dropdown column value from other table

Aplogies for posting a question which I think must be trivial but I
can not find the answer anywhere!

I have posted this to the ActiveScaffold forum but there seems to be
very little activity there, hopefully there is someone here willing to
help ?

I have two tables, Item and Category. Item belongs_to Category which
has_many Items. I am trying to code up an Item form where one of the
fields allows selection of a category.

My ItemController looks like this:

class ItemController < ApplicationController
active_scaffold :item do |config|
columns[:category].ui_type = :select

which makes the “category” field appear as a drop-down list.

My ItemHelper looks like this:

module ItemHelper
def category_column(record)
if record.category.nil?

def category_form_column(record,input_name)
options = Category.find(:all).collect do |c|
[ c.summary, ]
select :record, :category, options, {:include_blank =>
false, :prefix => input_name}

The category_form_column helper makes the correct category names
appear in the drop down.

The form is correctly rendered but when I commit, the record shows a
nil category_id and a nil @category.

What am I missing ? I’ve looked everywhere for an example but can’t
find one. I think an ActiveScaffold tutorial on this would be useful.

Thanks for any help…