Modifying Rails validator on runtime

model.rb

unique_email_validator = validators_on(:email).find { |v|
  v.is_a?(ActiveRecord::Validations::UniquenessValidator)
}

def unique_email_validator.validate(*users)
  return false if users.map(&:chatbox).all?

  return false unless app_users?(users.collect(&:email))

  super
end