singleton active record

hello, I am trying to define a singleton active record on a rails 3.1 app. What's missing please?

class Bitcoin < Currency   include ActiveRecord::Singleton

end

When I run Bitcoin.instance get this error:

NameError: uninitialized constant ActiveRecord::Singleton

Hi!

Your Currency class extends ActiveRecord::Base ?

Best Regards,

Everaldo

Found the answer. thanks. I had to install gem "acts_as_singleton"