It's possible to use @ViewChild (also @ViewChildren and @ContentChild/Children) to query for components of different types using dependency injection.
In the example below we can use @ViewChildren(Base) to get instances of Foo and Bar.
abstract class Base {}
@Component({
selector: 'foo',
providers: [{ provide: Base, useExisting: Foo }]
})
class Foo extends Base {}
@Component({
selector: 'bar',
providers: [{ provide: Base, useExisting: Bar }]
})
class Bar extends Base {}
// Now we can require both types of components using Base.
@Component({ template: `<foo></foo><bar></bar>` })
class AppComponent {
@ViewChildren(Base) components: QueryList<Base>;
}