title: Angular 2 - *ngFor with keys pipe is not refreshed when object is changed
body: <p>I'm using keys pipe in *ngfor loop. Data are fed in JSON.</p>
  
  <pre><code>    @Pipe({
        name: 'keys'
      })
      export class KeysPipe implements PipeTransform {
        transform(value, args: string[]): any {
          if (!value) {
            return value;
          }
  
          let keys = [];
          for (let key in value) {
            keys.push({key: key, value: value[key]});
          }
          return keys;
        }
     }
  </code></pre>
  
  <p>--</p>
  
  <pre><code>&lt;div *ngFor="let item of jsonObject | keys"&gt;
          &lt;p&gt;{{ item.value.code }}&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>The problem is when I delete on of the element in JSON, ngFor is not updated.</p>
  
  <p>I have tried two option already:</p>
  
  <ul>
  <li>calling <strong><em>this.applicationRef.tick();</em></strong> after element delete, no change</li>
  <li>impure pipe "<strong><em>pure: false</em></strong>". This caused enormous memory usage in chrome in hundreds of MBs and I had to kill the process.  </li>
  </ul>
  
  <p>If there any other way?</p>
  
  <p>Thanks!</p>