Question

If I have a nested categories, where each category might have many sub-categories, and each category belongs to one parent category, how would I write the Category model ?

I thought it will be something like this:

Category
belongs_to :category 
has_many   :categories

where I have parent_category_id in the category table, is this a good relationship ? or do I need a second table to present a many to many relationship ? I think I need some thing like belongs_to_and_has_many ?

Any guidance will be appreciated

Answer 1

class Category < ActiveRecord::Base

belongs_to :parent, :foreign_key => "parent_id", :class => "Category"
has_many :categories, :foreign_key => "parent_id", :class => "Category"

# Uses parent_id for the association.

has_and_belongs_to_many and a second table are not needed or appropriate for mapping this kinda structure.