title: How to use ngFor trackBy but notify about component input change?
body: <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div *ngFor="let obj of objs; trackby:objToId"&gt;
    &lt;sample-component [obj]="obj"&gt;&lt;/sample-component&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p><strong>Actual behaiviour :</strong></p>
  
  <ul>
  <li><code>sample-component</code> is not notifed about changes in obj attributes.</li>
  </ul>
  
  <p><strong>Desired behaiviour :</strong></p>
  
  <ul>
  <li><code>sample-component</code> should be notifed about any obj attribute change without rerendering component.</li>
  </ul>
  
  <p>How to achieve desired behaiviour ?</p>