Using @ViewChild in a component

app.component.ts

 @ViewChild(HelloComponent) hello: HelloComponent;
 @ViewChild('template') template: TemplateRef<any>;
 @ViewChild('element') element: ElementRef;
 @ViewChild('container', { read: ViewContainerRef }) container: ViewContainerRef;
   
 ngAfterViewInit() {
   console.log(this.hello);
   console.log(this.template);
   console.log(this.element);
   console.log(this.container);
 }