title: Trigger matAutocomplete programmatically
body: <p>I'd like to trigger autocomplete only if a special character is written at the end of the input text.</p>
  
  <p>E.g when the user types: '<code>@</code>', the autocomplete should appear.</p>
  
  <p>This is my code:</p>
  
  <pre><code>&lt;mat-form-field&gt;
    &lt;input #myInput type="text" matInput [formControl]="myControl" [matAutocomplete]="myInput.value.slice(-1) == '@' ? auto : false"&gt;
  &lt;/mat-form-field&gt;
  
  &lt;mat-autocomplete #auto="matAutocomplete"&gt;
    &lt;mat-option *ngFor="let option of options" [value]="option"&gt;{{option}}&lt;/mat-option&gt;
  &lt;/mat-autocomplete&gt;
  </code></pre>
  
  <p>The autocompleate appears, but does disappear automatically.
  Is there a way to do this?</p>