title: attr_accessor coming in empty in model
body: <p>I have a form with a field that does not live permanently on the model so I am using attr_accessor on the model to make it available for use, however it is always returning nil when I try to access it.</p>
  
  <p>The form field:</p>
  
  <pre><code>&lt;%= text_field_tag :discount_code, nil, maxlength: "12", class: "span2" %&gt;
  </code></pre>
  
  <p>The controller:</p>
  
  <pre><code>def an_action
     @job = Job.find(session[:job_id])
     @job.some_method
  end
  </code></pre>
  
  <p>The model:</p>
  
  <pre><code>class Job &lt; ActiveRecord::Base
      attr_accessor :discount_code
  
      def some_method
          if !self.discount_code.blank?
          do some logic
      end
  end
  </code></pre>
  
  <p>The above statement never executes as it is always evaluating to nil.</p>
  
  <p>The value of the field is available in the controller as a param w/out issue:</p>
  
  <pre><code>discount_code: test50
  action: process_payment
  controller: jobs
  </code></pre>
  
  <p>Any pointers would be appreciated.</p>