Rails - Apr 2005 - Tree - acts_as_tree

I have a table with the fields:
- id
- parent_id <- this field have the parent id
- position_id  <- this field have the id of the item above it
I''m using this fields to set a order in the list when create the tree, 
and one item can have many children and one parent.

What is right to use in the model, this?
* *   belongs_to :parent, :class_name => ''Media'',
:foreign_key =>
''parent_id''
    has_many :children, :class_name => ''Media'',
:foreign_key =>
''parent_id'', :dependent => true
or this?
    acts_as_tree :order => ''name'', :class_name =>
''Media'', :foreign_key
=> ''position_id''  
or somethink with?
    has_and_belongs_to_many :media
I really don''t understand it yet and how to make this tree correctily
in
order...
How i insert position_id in model, I need to do it?

Thank you..

-- 

Pedro C. Valentini
pedro-p14LI7ZcAE/pVLaUnt/cCQC/G2K4zDHf@public.gmane.org
+55 (21) 8708-8035

> * *   belongs_to :parent, :class_name => ''Media'',
:foreign_key =>
> ''parent_id''
>     has_many :children, :class_name => ''Media'',
:foreign_key =>
> ''parent_id'', :dependent => true
> or this?
>     acts_as_tree :order => ''name'', :class_name =>
''Media'', :foreign_key
> => ''position_id''
The latter is more correct.  While the first example may work, the
second is more concise and makes use of the auto-generated
acts_as_tree methods, "parent" and "children".  Normally,
it''s not
necessary to use the :class_name and :foreign_key fields in an
acts_as_tree definition, since it knows that you''re talking about the
model itself (the model in which you use the "acts_as_tree" method
call).  As far as I know :class_name doesn''t do anything, and
:foreign_key is only necessary if the parent_id field is called
something other than parent_id.

I think you may be wanting to do this:

class Media < ActiveRecord::Base
  acts_as_tree :order => ''position_id''
end

You will then be able to access Media objects in your controller (or
view) like this:

@my_media_object = Media.find(1)
for @medium in @my_media_object.children
  # Do something with each @medium object
end
> How i insert position_id in model, I need to do it?
Use the :order => "position_id" parameter.
> Thank you..
You''re welcome. Have fun!

Duane Johnson
(canadaduane)