Rails - Jan 2006 - Getting a user from a model (sort of a noob)

As mentioned in my previous posts I''m trying to create a dynamic  
directory for file_folumn. After finding out that I didn''t have the  
most recent version I installed the latest trunk and am able to get  
file_column to act as it should. However I have been racking my brain  
on how to implement finding my current user from a model. I have  
tried everything in my basic/getting better knowledge of Rails and  
Ruby but have been striking out so far no luck. I am assuming others  
have done this so just some tips on how to get at this info would be  
greatly appreciated. The model that I am trying to get at the user  
info from does have a belongs_to relationship to my user. Here is my  
last attempt which comes back with a user can''t be found without an  
ID=0 error:

File.join("test",User.find(self.user_id).companyname,"image")

I have also tried:

File.join("test",User.find(self.user.id).companyname,"image")

And receive the Called id for nil, which would mistakenly be 4 -- if  
you really wanted the id of nil, use object_id error message. By my  
knowledge this makes sense as the object that I am creating has not  
totally been saved yet but I thought that by calling an Object.new 
(params[:object]) that the object at least resides in memory at this  
point (I am doing the object.new at the beginning of my create method  
in the controller for that model). Am I on the right path here or  
just running around in circles?

Thanks for all the help from everyone on the list without it I would  
be having a much harder time than I am getting my head wrapped around  
Ruby and Rails (I am working under a deadline and have been forced to  
learn at the same time that I am writing a product for release for  
our company)

Andrew