title: Add method to rails model without restarting the server
body: <p>i am currently struggling with fixing an error in my rails application. Is it possible to add a method to a rails model. I have to admit that my rails skills are really basic.</p>
  
  <p>An example:
  My observations_controller.rb is calling </p>
  
  <pre><code>:trainingObs =&gt; observation_from_twitter.map { |o| { :category =&gt; o.rejected ? Do_something : Do_something_else}}
  </code></pre>
  
  <p>where observation_from_twitter is an array of observation objects. But unfortunately i still have to implement the method <code>rejected</code>. How do i now apply the change after adding the method to the model? And is that possible without restarting the server as stated in the title?</p>
  
  <p>Thanks</p>