Rails Virtual Attribute(s) Not Validating - ruby-on-rails

Question

I guess that in many ways I'm still a newbie with some of this rails stuff.
I have ActiveRecord Model for Payments.
But, it only has two things that get added to it's table and those are done once we get a positive response back from authorize.net.
In the Controller for this model I have my Cart form.
Within the Cart form I have billing information with default values pulled from #client and the credit card information. It looks a bit like this:
<%= form_for #payment, :url => { action: "checkout" } do |f| %>
...show errors ...
<%= f.fields_for #client do |ff| %>
<%= ff.label :firstname, 'First Name*' %>
<%= ff.text_field :firstname %>
...more fields ....
<%= ff.label :zip, 'Zip*' %>
<%= ff.text_field :zip %>
<% end %>
<%= f.label :cardnumber, 'Card Number*' %>
<%= f.text_field :cardnumber %>
... more cc info fields ...
<% end %>
Now in the Model I have added attr_accessor :cardnumber, and other card info fields.
I don't have any getter or setter methods for these (perhaps that is what I am missing).
However, I do have this in the Payment Model:
validates :zip, presence: true, numericality: true
validates :cardnumber, presence: true, numericality: true
Yet, so far the form will bypass this validation all together and goes direction to the checkout. Any help would be greatly appreciated! How do I get these validations to work properly?

Answer 1

If you want to get into the technical details, most of Rails' baked-in validators inherit from ActiveModel::EachValidator and this validator explicitly checks the attributes collection from ActiveModel via #read_attribute_for_validation. If #zip and #cardnumber have been set up with attr_accessor they are most likely not part of #attributes and thus skipped by the validator.
The simplest workaround would be to write a private method that validates zip/cardnumber and then call .validates with the name of that validation method. The pattern that was recommended by Koz would look like this...
class Payment
attr_accessor :zip
validate :assure_zip_not_blank
private
def assure_zip_not_blank
errors.add(:zip, 'cannot be blank') if zip_blank? && new_record?
end
def zip_blank?
self.zip.blank?
end
end
Separating the validation into two methods (assure_zip_not_blank and zip_blank?) may be overkill in this particular case but it's helpful when the logic becomes more complicated and/or you can reuse the logic.