Another NoMethodError

I have an ActiveRecord class called Foo that I've added some methods
to in the foo.rb file.
I have created an instance of Foo within another ActiveRecord Bar
within the file bar.rb.

I keep getting this error:
NoMethodError (undefined method `do_some_stuff' for #<Foo:0x3d61c14>):

I very clearly have a method:

class Foo < ActiveRecord::Base
   def do_some_stuff
       puts "I did some stuff"
   end
end

Is there something I'm missing that is causing this?
Do I have to call something to make this method available outside of
the class?

Thanks, Bob

Is there something I'm missing that is causing this?
Do I have to call something to make this method available outside of
the class?

nope. What does your actual code look like ?

Fred