I'd like to extend Ryan's code to order the tree by two conditions. The first, would be for each level of the tree to display in alphabetical order. The second condition would be a "sticky" boolean field included in each category that would take priority over the alphabetical order condition.

So, the output for a life tree would look like this:

- Animal
-- Mammal (sticky field is true)
--- Human (sticky field is true)
--- Dolphin
--- Whale
-- Bird
-- Dinosaur
-- Fish
- Plant
-- Flower
-- Tree
--- Oak

every nice tutorial on acts_as_tree

am using acts_as_tree and yui to generate tree structure,
as per the DB is consern for acts_as_tree,the parent and child nodes are from one table..

i have two different table like

region table
-------------
pk     name       
1      hyderabad
2      chennai
3      bangalore

area tabel
id     name          fk
1      madhapur      1
2      hi-tech       1
3      kondapur      1
4      adayar        2
5      ECR road      2
6      anna nagar    2
7      whitefiled    3
8      MGM           3

so i need name in region table as root node and the respective fk names in area table as child nodes(i dont need subchild node )..

how can i use acts_as_tree for this table,are is there an alternative to do this

A piece of code from the schema:
create_table "regional_objects", :force => true do |t|
    t.string   "name"
    t.integer  "parent_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

class RegionalObject < ActiveRecord::Base
  acts_as_tree :order => "name"
#the rest of associations is deleted just for the example
end

<% if @regional_objects.empty? %>
  <h4> No Granting regions found</h4>
<% else %>
  <h4>Listing Granting regions</h4>
  <%= render :partial => 'regional_object', :collection => @regional_objects%>
  
  <%= will_paginate @regional_objects %>
<%end%>
<br />
<%= link_to 'New granting region', new_regional_object_path %>

<table>
  <td><%= h regional_object.name%></td>
  <td><%= link_to 'Sub-Regions', regional_object%></td>
  <td><%= link_to 'Edit', edit_regional_object_path(regional_object)%></td>
  <td><%= link_to 'Destroy', regional_object, :confirm => 'Are you sure?', :method => :delete%></td>
</table>

<p>
  <b>Name:</b>
  <%=h @regional_object.name %>
</p>
<%if @regional_object.children.empty?%>
  <h4>No sub regions found</h4>
<%else%>
  <%= render :partial => 'regional_object', :collection => @regional_object.children %>
<%end%>
<br/>
<%= link_to 'Add', new_regional_object_path%>|
<%= link_to 'Back', regional_objects_path %>

<% form_for @regional_object do |form| %>
  <%= form.error_messages %>
  <h1>Create a Sub-Region for <%=h @regional_object.parent.name%></h1>
  <p>
    <%= form.label :name, "Sub-Region" %><br />
    <%= form.text_field :name %>
  </p>
  <p>
    <%= submit_tag "Create" %>
  </p>
<% end %>
<%= link_to 'Back', @regional_object.parent %>

map.resources :products, :has_many => :packagings

Showing app/views/reporter/_side_nav.rhtml where line #10 raised:

undefined method `children' for ReportGroup:Class

Extracted source (around line #10):

7:    </ul>
8:
9:     <li><%= link_to ReportGroup.name, {:controller => 'reporter', :action => "list_reports", :id => ReportGroup.id } %></li>
10:     <% if ReportGroup.children.empty? %>

db(report_groups)

'id', 'int(11)', 'NO', 'PRI', '', 'auto_increment'
'name', 'varchar(255)', 'YES', '', '', ''
'parent_id', 'int(11)', 'YES', '', '', ''
'position', 'int(11)', 'YES', '', '', ''

class ReportGroup < ActiveRecord::Base
  acts_as_tree :order => "name" 
end

class ReporterController < ApplicationController
  def index
    @page_title = 'Reporter Dashboard'
    @statistics = Stat.find(:all, :order => "name")
    @graphs = Graph.find(:all, :order => "name")
    @report_groups = ReportGroup.find:all
  end

<% content_for :side_nav do %>
    <%# TODO: move reporter side_nav in here when it's considered complete %>
    <%= render :partial => 'reporter/side_nav' %>
<% end %>
<% session[:layout] = :reporter %>
<% inside_layout 'application' do %>
    <%= yield %>
<% end %>

<p>
  Standard Reports
  
   <ul>
     <%= render :partial => 'report_group', :collection => ReportGroup.find_all_by_parent_id(nil) %>
   </ul>
    <li><%= link_to ReportGroup.name, {:controller => 'reporter', :action => "list_reports", :id => ReportGroup.id } %></li>
    <% if ReportGroup.children.empty? %>
      <span> No sub</span>
      <% else %>
        <ul><%= render :partial => 'report_group', :collection => ReportGroup.children %></ul>
        <% end %>
      <ul>
        <% ReportGroup.standard_reports.each do |sr| %>
          <% if rg.name.downcase == 'summary'%>
            <li><%= link_to sr.name, {:controller => 'reporter', :action => 'show', :id => sr.id }%></li>
          <% end %>
        <% end %>
      </ul>
  </ul>
</p>

Cool, Thanks ryanb... I assume it is possible to display it in a drop down?

Yeah it's certainly possible, but the difficulty depends on what you want to do (have it sorted properly with indents is kind of hard). I recommend starting a separate thread on this if you need to do this.

Thanks again

Also, looks like you're using zero as the root parent_id value. In that case the find by "nil" won't work, you'll need to either find by "0" or change your table content.

Newbie here

The top child is easy to do, as I just check item.position == 0. However, the bottom one is trickier. Currently I run a query to check if the position of the item is equal to the max position for that set of children.

I'm hopeful that there's some nice Ruby/Rails feature like item.last? that would work for me. If I could access the collection that gets looped in the partial, I could do something like item == collection.last, but I don't know how to access the collection from the partial.

Any suggestions?

Thank you very much for your reply.

Question 1:
-----------
Example of my scenario is as follows:

                                               Group-1
                                                     |
                ------------------------------------------------------------------------------
                |                           |              |            ..   |                           ..   |      ..|
          Group-2                       Group-3         Group-4                                                                     Group-9
                                            |                                       |
                 -------------------------------------------------------           User-9   
                 |            |             |            |             |                 
           Group-3.1      Group-3.2     Group-3.3     User-3.1     User-3.2         
                 |
        ----------------
        |              |
Group-3.1.1       Group-3.1.2

Note: 
1.  Group can have sub-groups.  I have Group model with parent_id.
2.  User is under a group.  I have User model with group_id.
3.  Group/sub-group can have zero or more users.
4.  The tree above shows that user cannot have sub-group under it.
5.  I have multiple layers of groups and sub-groups.

How can I display these 2 models - Group and User in the same tree structure.

Question 2:
-----------
Based on the partial code in the earlier post, I tried the following.  But, I encountered error saying Nil is encountered in the 2nd line of _group.html:

Group controller:

def list
  @parent_id = ?? # where ?? = id set by other part of the controller
  @group = Category.find_all_by_parent_id(@parent_id)
  if @group.empty?
    #... display NO SEARCH RESULTS
  end
end

list.rhtml:

<%= render :partial => 'group', :collection => @group %>

_group.rhtml:

As per the partial code in the earlier post, where the 2nd line reads as:
  <%= link_to h(group.name), :controller => 'group', :action => 'show', :id => group.id %>

<%= @parent_group.name %>
<% for group in @parent_group.children %>
  <%= group.name %>
<% end %>
<% for user in @parent_group.users %>
  <%= user.name %>
<% end %>

I have 2 models: Group and User.
- Group has these fields:  id, name, parent_id.
- User has these fields:   id, name, group_id.

what I need is:
1.  User to enter the (parent) group that s/he wants to see.
2.  I need to display the (parent) group as entered by user, then the children groups, and lastly the users under the (parent) group.

Thank you very much for your help.

Regarding the "toggle children" function, pls enlighten me how to write the code to allow toggling of the children records.

Thank you.

btw, i really enjoy your podcasts!