Basically, the scope adds a condition to the queries, but since you don’t know the foreign_key id ahead of time for the related Model’s record you are limited when using $actsAs to setting either a static value..

i.e. ‘scope’ => array( ‘RelatedModel.field’ => 23 )

*OR* you can attach and detach on the fly ala
http://www.mcfarren.org/CodeCakePHPStoringMultipleTreesWithTreeBehavior

I found another behavior for this on the Bakery but decided to use yours because it seems to deviate less from the core.

(other behavior:
http://bakery.cakephp.org/articles/view/scopedtreebehavior
)

As for the scope option – yes and no. Scope for TreeBehavior can be used to add simple find conditions, just like counterScope for counterCache. But you can also pass the name of an associated belongsTo model, as TreeBehavior::setup() shows. Since this feature is undocumented, I had thought (naively perhaps) that it would add a find condition to reordering operations so that only other records in the table with the same belongsTo foreign model would be affected.

So, you pass a “NavList” as the scope and TreeBehavior ensures that only NavItems with the same nav_list_id as the record you’re manipulating get included in tree-restructuring. But obviously that didn’t turn out to be the case. Instead placing a condition like this on reordering operations:

NavItem.nav_list_id = 7 // assuming “7″ is the nav_list_id for the current record

The stock TreeBehavior just inserts this:

NavItem.nav_list_id = NavList.id

which is useful in some cases but not when you want to maintain separate trees within the same table.

Also, this just got posted on the Bakery : http://bakery.cakephp.org/articles/view/btree-behavior ?