title: Angular 2 referencing dynamic instance of @ContentChild
body: <p>I'm using Angular 2.0.1.</p>
  
  <p>I have a component that can take in any other component via <code>&lt;ng-content&gt;</code> -- this works great.</p>
  
  <p>The issue I run into is when I want to reference the injected component.</p>
  
  <p>If I knew that <code>&lt;ng-content&gt;</code> would only ever be one component I could say:
  <code>@ContentChild(MyComponent) dynamicTarget: IMyComponent;</code> but because it could be <em>any</em> component (the only assumption I would make is that any injected component implements a specific interface) it become trickier.</p>
  
  <p>I've also tried <code>&lt;ng-content #dynamicTarget'&gt;</code> and then referring to it by saying  <code>@ContentChild('dynamicTarget') dynamicTarget: IMyComponent;</code> but this returns undefined.</p>
  
  <p>Does anyone know how I could tell Angular 2 that this thing is an instance of a component so that I can attempt to call a function on it?</p>
  
  <p>To further clarify the use case -- I have a multi-step wizard that could take in any component as content, and I want to call the <code>validate</code> function on the content (which again, I would assume exists on said instance)</p>