title: How to share a method between classes defined via Ruby Struct?
body: <p>Given a set of classes defined using Structs, like :</p>
  
  <pre><code>K1=Struct.new(:a,:b)
  K2=Struct.new(:c,:d)
  ...
  </code></pre>
  
  <p>is it still possible to add a single common method :foo to every class defined that way, or do I need a deep refactoring ? </p>
  
  <p>Factoring such behaviors is normally done using inheritance (or mixins), but I don't know if such a factoring is now still possible, starting with such struct-based class definitions.</p>