Custom Validation Classes in Ruby on Rails -

I am trying to create a custom recognition class on the rail in Ruby, though I can not know how to make it modular.

I followed this example:

For another example on that page: "Validate the single state of the object with a distinct custom verifier" how do I put the PreventFutureDateValidator class in a different file Can i I did not know where these files would be placed in the Ruby on Rails.

These types of files are usually stored in / lib . >