title: Max value from multiple ActiveRecord relations
body: <p>I have a group of 5 AR objects each from a different model however each has a common field being likes_count</p>
  
  <p>I would like to identify the AR object with the greatest value in likes_count</p>
  
  <pre><code>a = Student.where("likes_count &gt; 0").order_by("likes_count DESC").first
  b = Teacher.where("likes_count &gt; 0").order_by("likes_count DESC").first
  c = Class.where("likes_count &gt; 0").order_by("likes_count DESC").first
  d = School.where("likes_count &gt; 0").order_by("likes_count DESC").first
  </code></pre>
  
  <p>I could achieve this with a if statements however this will be very messy. Is there an easier way ?</p>
  
  <p>It is theoretically possible that each object will be nil.</p>