title: Subinstances sharing a common superinstance
body: <p>I have a class Super and several subclases Sub1, Sub2,...</p>
  
  <p>Is there a way to instantiate objects sub1, sub2 that would share the same super instance?</p>
  
  <p>The situation comes from an inner nested class configuration like this:</p>
  
  <pre><code>Super{  
      superFields...
      Sub1{...}
      Sub2{...}
      ........
      }
  </code></pre>
  
  <p>But the inner claeses have grown too much, and I woud feel more confortable having them in separate files. They need to share the same instance of superFields, so my question.</p>