title: How to detect change to a property in Angular
body: <p>I have a component with a sub component <code>timeline</code>.</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;app-timeline [(editing)]="editingDate"&gt;&lt;/app-timeline&gt;
  </code></pre>
  
  <p>In the timeline component I have these properties:</p>
  
  <pre class="lang-ts prettyprint-override"><code>@Input() editing: boolean; // &lt;--- detect change on this
  @Output() editingChange = new EventEmitter();
  </code></pre>
  
  <p>How can I check when a change to the <code>editing</code> property occurs from the timeline component? I need to emit the editing value whenever it changes.</p>
  
  <p>Should I use a setter for the editing property then emit from there?</p>
  
  <pre class="lang-ts prettyprint-override"><code>private _editing
  set editing() { ... // emit }
  </code></pre>
  
  <p>Or is there another way? </p>