title: How to perform an inclusion validation on a serialized attribute?
body: <p>I have a model with an serialized attribute (array). I would like to validate the model only if each member of the array is included within the pre-determined options.</p>
  
  <p>Example: 
  I have a Person model which has a "mood" attribute. Users can have more than one mood, but each mood must be either 'happy', 'sad', 'tired' or 'angry'.</p>
  
  <p>The model would be something like this:</p>
  
  <pre><code>class Person &lt; ActiveRecord::Base
    MOODS = %w[happy sad tired angry]
    # validates :inclusion =&gt; { :in =&gt; MOODS } 
  
    attr_accessible :mood
    serialize :mood
  end
  </code></pre>
  
  <p>The commented validation doesn't work. Is there any way to make it work or do I need a custom validation? </p>
  
  <p>(Note: I don't want to create a separate Mood model.)</p>