Which associations should I use? to extend ad model

Rails
1

I would like to use only one table ads on database.

regular AD:

:from
:to

Which associations should I use?
Polymorphic Associations
The has_and_belongs_to_many
Else?

2

I create a Gist with my recent ideas: sti ยท GitHub
** http://groups.google.com/group/rubyonrails-talk?hl=pl

3

what are the other objects? What is it that has_and_belongs_to_many?
for polymorphic relationships you want to ask if more than one
So
class Ad
belongs_to :adable, :polymorphic => true
end

class Customer
has_many :ads, :as => :adable
end

class NewsPaper
has_many :ads, :as=>:adable
end

At least I think this is what you are looking for. Maybe some others
will give advice.

4

I think form me i should be something like this below because I need
different validations to each type of ads. Or in your example could i
set
up this kind of different validations?

:category_id
:admin_id
:price
:display_counter
:type
end

class RegularAd < Ad

validates_presence_of :title, :ad_content

:title
:ad_content
end

class RideAd < Ad

5

STI , Single Table Inheritance (This structure is best used for
models that have identical, or very similar attributes )

trip AD << regular AD

class RegularAd < ActiveRecord::Base
end
class TripAd < RegularAd
end

migration (Rails 3.1)
class CreateAds < ActiveRecord::Migration
def change
create_table(:regular_ads) do |t|
t.string : title
t.float : price
t.string : content
t.string : username
t.integer : from
t.integer: to
end
end
end