stuff placed in application_helper.rb is only available to your
Views / Helpers.
If you want a constant to be available to everything put it in your
Or if you only need it in your controllers controller/application.rb.
Just models you can create a module in your /lib folder and mix it in
with ActiveRecord::Base to make it available to all your models.
I know you wanted them all but I figured I'd just cover the others as
Hope I helped,