title: Angular FormArray display validation errors
body: <p>I have Angular form that is built with help of FormBuilder.</p>
  <p>Form contains a FormArray which has as many fields as user wants. I've set validator for fields</p>
  <pre><code>this.fb.array([this.fb.control('', Validators.required)])
  </code></pre>
  <p>and for each new <code>push</code> validator is the same.</p>
  <p>The problem is that I don't know how to access a specific field's <code>isValid</code> property since they are bound with <code>FormControl</code> via <code>[formControlName]=&quot;index&quot;</code>.</p>
  <p>I've tried to do it that way, but it doesn't seem to work</p>
  <pre><code>&lt;div *ngIf=&quot;array.at(index).invalid&quot; class=&quot;alert alert-danger p-2&quot;&gt;
  &lt;/div&gt;
  </code></pre>
  <p>Where <code>array</code> is a <code>formArray.controls</code> passed from a parent.</p>
  <h1>Update #1</h1>
  <p>There is a case <a href="https://stackblitz.com/edit/angular-7ppkoh" rel="noreferrer">https://stackblitz.com/edit/angular-7ppkoh</a></p>