Calling RESTful 'scoped' INDEX when params[] is no

I have a VERY hierchical database and am using a RESTful
approach. Normally, when users’ enter the system they’ll cascade
level to level in the database and thus the hierchical information
such as child.parent.grandchild_id are always available to the
However, when I attempt to directly call a middle level table.index I
obviously fail, because the parent_id is not available to pass to the
RESTful route.
I’d like to have a ‘safety mechanism’ built into my code that handles
this by simple displaying all records irrespective of
Here is an example of my before_filter event and the way I use it
to call my index:

def find_parent
@find_parent || @project = Project.find(params[:project_id])

Here is a typical table.index action:

def index
@portals = @project.portals.find :all

Would it be possible to make the INDEX code something like this;

def index
if @project.nil?
@portals = Portal.find :all
@portals = @project.portals.find :all,

Fundumentally, what 'blows my mind' is that the 'find_parent'

‘before_filter’ event ALWAYS has to fire and if no parent exists, I
can’t see how to return a ‘[email protected]’ or whatever is needed to
the if, else routine (above)?

Thank you,