title: Angular Dark Theme
body: <p>Hello I have made a toggle button that changes my Ionic 3 app to dark mode. But I don't know where to define the global class <code>[class.dark-theme]="dark"</code>. It must be on app.component.ts to make the change in the whole app. This is what I have so far:</p>
  
  <p>any-page.html</p>
  
  <pre><code>&lt;ion-item&gt;
      &lt;ion-label&gt;
        Dark Mode
      &lt;/ion-label&gt;
      &lt;ion-toggle [(ngModel)]="dark"&gt;&lt;/ion-toggle&gt;
    &lt;/ion-item&gt;
  </code></pre>
  
  <p>variable.scss</p>
  
  <pre><code>.dark-theme
  {
    ion-label{
      font-size: 33pt;
    }
  }
  </code></pre>
  
  <p>app.component.ts</p>
  
  <pre><code>export class MyApp {
    dark=false;
  }
  </code></pre>
  
  <p>How should I define the class for <code>NgModel="dark"</code> <code>([class.dark-theme]="dark")</code></p>