Rails gem for modifying model’s attributes before validation.

class Person < ActiveRecord::Base
  modify :first_name, :last_name do |old_value|
    old_value.upcase
  end
end

p = Person.new :first_name => 'John', :last_name => 'Doe'
p.first_name #=> John
p.last_name  #=> Doe
p.valid?
p.first_name #=> JOHN
p.last_name  #=> DOE