Self-referencing model

I'm fairly new to Ruby on Rails, and am having trouble figuring out how
to do this. I have a model called Organization. I want to set things
up so that an org can have sub-orgs (which can have sub-orgs
themselves).

Can anyone point me to a good example or explanation (or provide one
directly) so I can get an idea of how to do this?

Thanks!

I've just been doing this myself with systems and sub-systems.

In the system model I have:

  has_many :sub_systems, :class_name => "System", :foreign_key =>
"system_id", :dependent=>:nullify

Then you can refer to the system.sub_systems

I also have code to prevent loops which will go around forever if you
traverse the system-sub-system tree.

def validate
    errors.add(:sub_systems, "Cannot be a subsystem of itself.") if
all_subs.include?(self)
  end

def all_subs(subs = [])
    self.sub_systems.each do |s|
      unless subs.include?(s)
        subs << s
        s.all_subs(subs)
      end
    end
    subs
  end

Hope that helps.

Look into the :as and :source options for the has_many and belongs_to
associations, they should be able to do what you need.

Good luck!

I forgot this - you also have to have

belongs_to :system

Acts as Tree:

http://wiki.rubyonrails.org/rails/pages/ActsAsTree

Does everything you need.