gistfile1.rb

require 'rubygems'
require 'not_naughty'

# Load the validations you want to use.
NotNaughty::Validation.load 'length', 'presence'

Person = Struct.new(:name) do
  extend NotNaughty
  validates(:name) { presence and length :minimum => 4 }
end

Person.new('Horst').valid? # => true
Person.new('Foo').valid? # => false