Validate fields only if virt_attribute is false - ruby-on-rails

Question

I have such model:
class Order < ActiveRecord::Base
attr_accessible :**** :phone_number, :receiver, :shipping_id, :street, :totalcost, :user_id, :zip, :use_user_data
attr_accessor :use_user_data
validates :city, :presence => {:message => I18n.t(:city_not_chosen)}
validates :zip, :presence => {:message => I18n.t(:zip_not_chosen)}
validates :street, :presence => {:message => I18n.t(:street__not_chosen)}
validates :building, :presence => {:message => I18n.t(:building_not_chosen)}
validates :phone_number, :presence => {:message => I18n.t(:phone_number_not_chosen)}
validates :receiver, :presence => {:message => I18n.t(:receiver_not_chosen)}
end
As you can see i set in model some field which is non-db field (use_user_data) - virtual attribute...
But how to do, if :use_user_data is false, good and right validate, but when true didn't validate?
i try so:
validates :city, :presence => {:message => I18n.t(:city_not_chosen)}, :unless => :use_user_data
and so
with_options :unless => :use_user_data do |order|
order.validates :city, :presence => {:message => I18n.t(:city_not_chosen)}
end
but it doesn't help me... Why?
Also my form:
= form_for #order do |f|
%div
= f.label :use_user_data , "Использовать данные вашего профиля*: "
= label :use_user_data , "Да"
= f.radio_button :use_user_data, true, :required => true, :id => "use_user_data", :checked => true
= label :use_user_data , "Нет"
= f.radio_button :use_user_data, false, :required => true, :id => "dont_use_user_data"
Also when i write
validates :city, :presence => {:message => I18n.t(:city_not_chosen)}, :if => :use_user_data
i get validation messages... But how to do only if false? And why my solution didn't work?

Answer 1

The form passes "true" or "false" string to the object, not boolean true or false. Since it's a virtual attribute, no typecasting performed. In Ruby, both "true" and "false" are true, so you need to use something to typecast the value
with_options :unless => Proc.new{ |a| a.use_user_data == 'true' } do |order|
order.validates ...
end
Or
with_options :unless => :use_user_data? do |order|
order.validates ...
end
def use_user_data?
use_user_data == 'true'
end

Answer 2

You need to put your :if or :unless conditions in a lambda or Proc.
validates ..., :if => Proc.new { |a| a.use_user_data === false }
This causes the check against :use_user_data to not be evaluated until the above validates line is executed during validation (the Proc is passed as the value to the :if or :unless option to be evaluated by Rails). The Proc will receive the current model attributes as an argument, allowing you to check those attributes (in this case, :use_user_data being false).