title: Cascading dropdown fill method running more than one in Angular 7
body: <p>I have an angular app. And I'm using cascading combobox (country-state) in below example. But, <code>get states()</code> method in <code>state.component.ts</code> running a lot of time. What can be the reason of this? I want run only country selection changed. I put <code>debugger</code>. You can reproduce bug by open console with F12.  <strong>If my method mistake, I can change completely my way.</strong></p>
  
  <p><a href="https://stackblitz.com/edit/angular-epvhvg?file=src/app/state/state.component.ts" rel="nofollow noreferrer">Stackblitz</a></p>