block20.ts

@Component({
  selector: 'my',
  template: `
    {{count}}
  `
})
export class MyComponent {
  @Input()
  count:string
}

@Component({
  template: `
    <my [count]="parentCount"></my>
    <button (click)="clickMe()">Click</button>
  `
})
export class AppComponent {
  parentCount=0
  clickMe() {
    this.parentCount++
  }
}