Hi! I have a problem with belongs_to and has_many, the thing is i have a category table which points to herself if it's a subcategory of another category.
I just started using ruby on rails, and don't know how to implement that or if it can be done (I assume it can).
Thank for any help.
You assume correctly. Here's an example:
class Category < ActiveRecord::base belongs_to :parent_category, :class_name => 'Category', :foreign_key => 'parent_category_id' has_many :subcategories, :class_name => 'Category', :foreign_key => 'parent_category_id' end
Your migration might contain this (among other stuff):
create_table :categories do |t| t.column :parent_category, :integer end
And now you can theoretically do things like:
subs = Category.find(1).subcategories parent = Category.find(2).parent
-Bill
Woops - that, of course, should have been:
t.column :parent_category_id, :integer
My bad.
-Bill
And this should have been:
parent = Category.find(2).parent_category
Sorry for the extra messages. I wasn't being as careful and thorough as I should have been.
-Bill
Great!! Thanks for a quick answer!
Quoting Adam <anlauf.adam@gmail.com>:
Hi! I have a problem with belongs_to and has_many, the thing is i have a category table which points to herself if it's a subcategory of another category.
I just started using ruby on rails, and don't know how to implement that or if it can be done (I assume it can).
Look at acts_as_tree. It's a plugin in Rails 2.0, builtin in Rails 1.2.
Example:
class Task < ActiveRecord::Base has_many :comments, :dependent=>:destroy end
class Comment < ActiveRecord::Base belongs_to :task acts_as_tree :order=>'created_at' end
Tasks have a hierarchy of comments with replies and replies can have replies arbitrarily deep.
task = Task.find(id) task.comments # top level comments task.comments[0].comments # replies to first top level comment
comment is like a category, reply is like a sub-category.
HTH, Jeffrey
OK, thanks!! I'll look that up too.