Rails - Jun 2006 - Overriding a file_column attribute in model

I have a user model subclassed into Employees and Managers using STI. I 
am using FileColumn to manage images, in this case logos. If an Employee 
doesn''t have a logo of its own, I want my app to use the
Manager''s logo
in views.

I did the following in models/users.rb:
-------

class User < ActiveRecord::Base
  file_column :logo
end

class Employee < User
  belongs_to :Manager
  def logo
    self[:logo] || self.manager[:logo]
  end
end

class Manager < User
  has_many :employees
end

-------

When I call <%= @user.logo %> and @user is an Employee, it returns the 
correct filename, using the Employee''s when one is set, and otherwise 
falling back on the Manager''s.

However, none of the file_column methods are available. All I''m getting
in @user.logo is a string. @user.logo.relative_path, for instance, 
returns nil, as do calls to url_for_file_column. Obviously all my 
accessor is returning is a string attribute, noit a file_coilumn. Is 
there a sensible way in my model to get the behavior I want, i.e. to 
override the default read accessor and return a file_column with the 
methods and attributes automagically brought along?

I suppose I could replace instances of url_for_file_column with a custom 
helper that checks the user object type and generates a 
url_for_file_column for either the Employee or Manager as needed, but I 
also use this in an ActionMailer template, and bringing view helpers 
into there gets ugly.

Thanks.

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