Rails - Jun 2006 - ActiveRecord has_one default value

My apologies if this is a dumb question, but I''ve searched around and 
haven''t been able to come up with a solution.

Is there a way when specifying a has_one association to specify a 
default value for an object if data is missing in the child table. For 
instance:

class Student
  has_one :university
end

if no university is associated to the student in the database, I would 
like to automatically return an instance of NoUniverisity class instead 
of it being set to nil. Similar to the NullObject refactoring described 
in Fowler''s book.

Any ideas?

Thanks!
Jay

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Jay Turpin wrote:
> class Student
>   has_one :university
> end
> 
> if no university is associated to the student in the database, I would 
> like to automatically return an instance of NoUniverisity class instead 
> of it being set to nil. Similar to the NullObject refactoring described 
> in Fowler''s book.
Warning - untested code:

class Student < ActiveRecord::Base
   has_one :university

   def university_or_default
     old_university || NoUniversity.new
   end

   alias_method :old_university, :university
   alias_method :university, :university_or_default

end

hth

-- 
R.Livsey
http://livsey.org