title: Angular2 - Simple changes QueryList
body: <p>Is there a way to get simple changes on a QueryList? I have a list of childcomponents which I hold in a querylist. I want to check which childcomponent has been added to the list (in an onchange event).</p>
  
  <p>Parentcomponent:</p>
  
  <pre><code>   @ContentChildren(forwardRef(() =&gt; ChildComponent), { descendants: true })
      private childComponents: QueryList&lt;ChildComponent&gt;;
  </code></pre>
  
  <p>When I click on a button a childcomponent gets added to the dom so the querylist changes triggers.</p>
  
  <p>When I subscribe to the querylist like so:</p>
  
  <pre><code>this.childComponents.changes.subscribe((changes) =&gt; {
          //here i just get the updated list. I don't have the previous list to compare.
  });
  </code></pre>