app.component.ts

@Component({
  selector: 'my-app',
  template: `
    <h1>Envie seu feedback</h1>
    <form [formGroup]="form" (ngSubmit)="onSubmit()">
      <div>
        <label>
          Sua avaliação:
          <app-star-rating formControlName="rating"></app-star-rating>
        </label>
      </div>
      <div>
        <label>Quer informar um comentário?</label>
        <input formControlName="comment" />
      </div>
      <button type="submit" [disabled]="form.invalid">Submit</button>
    </form>
  `,
})
export class AppComponent {
  form = new FormGroup({
    rating: new FormControl(
      { value: null, disabled: false },
      Validators.required
    ),
    comment: new FormControl(''),
  });

  onSubmit(): void {
    console.log(this.form.value);
  }
}