@Component({
  selector: 'app-unsorted-heroes',
  template: `
{{hero.name}}
`,
  providers: [HeroService]
})
export class HeroesBaseComponent implements OnInit {
  constructor(private heroService: HeroService) { }
 
  heroes: Array;
 
  ngOnInit() {
    this.heroes = this.heroService.getAllHeroes();
    this.afterGetHeroes();
  }
 
  // Post-process heroes in derived class override.
  protected afterGetHeroes() {}
 
}