Ruby on Rails

Okay, Thiagocifani and others interested,

I have finally revised the structure of my application for plural table names, which already existed,  and singular model names.  Across tables I have set up parent and foreign key with exactly the same field name and data type.  Within models I have defined belongs_to and has_many. 

Now I am revisiting my views, in the case where the child value is a single value to the parent, the display is working fine.   What I am finding challenging is populating <select  

The parent is advertiser, and the child is category..

Currently I have:

    <label>Advertisement Category:</label>
    <% @categories = Category.find(:all, :readonly => true, :order=> "category_type") %>
    <% @cats = options_from_collection_for_select(@categories, :category_id, :category_type) %>
    <%= nf.select( :category_id, @cats) %>

How do I rewrite this?  From the controller, how should I set up my data source?  Tried includes and Parent.child.find

Thanks,

Liz