Converting Acts_As_Tree to Acts_As_Nested_Set

Hello,

I have a tree structure that needs to be converted into a nested set.
A great deal of work has already been done on the tree items, so
maintaining the integrity of the id's is mandatory. However I need
the ability to access entire branches of the tree, which is what
Nested set does. Does anyone have any suggestions on how to
efficiently transfer the tree to the nested set and create the left
and right boundaries?

Thanks!

Awesome_Nested_Set looks interesting as well. Maybe I should use
that?

anyone have any ideas?

Mindtonic wrote:

anyone have any ideas?

You should definitely use awesome_nested_set instead of
acts_as_nested_set. The former has much cleaner code.

If the size of your tree allows it, I would choose to recreate it using
awesome_nested_set using move_to instead of figuring out a smart
algorithm for conversion. It'll spare you development time and guarantee
a proper conversion.

Is awesome_nested_set a better choice than better_nested_set? I found
the following on the better_nested_set wiki page:

Migrating from acts_as_tree

In reference to migrating from acts_as_tree Krishna Dole said, “If you
have multiple trees in your table, it is a little more complicated.
You first need to give each tree scope (add a tree_id column) and then
run the above method on a member of each tree.”

Not completely understanding that statement, I set out to implement it
in a migration. Here is my result which appears to work. In this
example, I am using a model named Categories:

class ConvertCategoriesToNestedSet < ActiveRecord::Migration
  def self.up
    add_column :categories, :lft, :integer
    add_column :categories, :rgt, :integer
    add_column :categories, :root_id, :integer

    # Convert existing tree to nested set with scope
    Category.reset_column_information # So the new root ids get saved
    Category.renumber_all
    Category.roots.each do |r|
      r.all_children.each do |c|
        c.update_attribute(:root_id, r.id)
      end
      r.update_attribute(:root_id, r.id)
    end
  end

  def self.down
    remove_column :categories, :lft
    remove_column :categories, :rgt
    remove_column :categories, :root_id
  end
end

Mindtonic wrote:

Is awesome_nested_set a better choice than better_nested_set? I found
the following on the better_nested_set wiki page:

Yes. Use awesome_nested_set instead.

Migrating from acts_as_tree

In reference to migrating from acts_as_tree Krishna Dole said, �If you
have multiple trees in your table, it is a little more complicated.
You first need to give each tree scope (add a tree_id column) and then
run the above method on a member of each tree.�

Not completely understanding that statement, I set out to implement it
in a migration. Here is my result which appears to work. In this
example, I am using a model named Categories:

Never read and thought of that, but that should work great!

Every time I tries to run the migration, the rake aborted saying that
there is a missing attribute 'name', which is definitely present in
the model. Also, the awesome_nested_set rdocs fail to rake...
rendering the concept useless as there is very little online
documentation. Oh well...

SOLUTION:

You're not going to believe this.

1. Install the plugin
2. Write and run a migration to add `lft` and `rgt` integer columns to
your model
3. Change `acts_as_tree` to `acts_as_nested_set` in your model
4. Open the Console
5. type: NameOfYourModel.rebuild!

That's it!

Woah, I've been looking for this for weeks. I hope it helps somebody
out there.