Thanks for the explanation.
What if I wanted to add categorization to listing where categories has these fields:
t.column :categories, :name, :string
t.column :categories, :parent_id, :integer
and I wanted to add the above as an acts_as_tree too to the listing model:
add_column :listings, :category_id, :integer
add_column :listings, :subcategory_id, :integer
If its acts_as_tree , then is it habtm or just a plain has_many?
class Category < ActiveRecord::Base
class Listing < ActiveRecord::Base
Thanks for the help. I'm just trying to master associations and I'm confusing myself sometimes.