ContentChild by extended abstract class

Question

I have two different components that extend a common one.

AComponent extends BaseComponent {}
BComponent extends BaseComponent {}

There is a third component that has ng-content.

<wrapper>
  <a-component></a-component>
  <b-component></b-component>
</wrapper>

Unfortunately those component aren't visible in below scenario.

WrapperComponent {
  @ContentChildren(BaseComponent) components;
}

I don't want to create ContentChild with specific types (Acomponent, BComponnet).

Answer 1

you can use Alias providers as a workaround.

Define your components as follows;

@Component({
  selector: 'a-component',
  templateUrl: './a.component.html',
  styleUrls: ['./a.component.css'],
  providers: [{ provide: BaseComponent, useExisting: AComponent }]
})
export class AComponent extends BaseComponent implements OnInit {
  constructor() {
    super();
    console.log("a created.");
  }

  ngOnInit() {}
}

and

@Component({
  selector: 'b-component',
  templateUrl: './b.component.html',
  styleUrls: ['./b.component.css'],
  providers: [{ provide: BaseComponent, useExisting: BComponent }]
})
export class BComponent extends BaseComponent implements OnInit {
  constructor() {
    super();
    console.log("b created.");
  }

  ngOnInit() {}
}

where BaseComponent is

export abstract class BaseComponent {}

use it in the WrapperComponent as follows

@Component({
  selector: 'wrapper',
  templateUrl: './wrapper.component.html',
  styleUrls: ['./wrapper.component.css']
})
export class WrapperComponent implements OnInit, AfterContentInit {
  @ContentChildren(BaseComponent) components;

  constructor() { }

  ngOnInit() { }

  ngAfterContentInit() {
    console.log("components: ", this.components.length);
  }
}

here is a working demo https://stackblitz.com/edit/angular-ynqhwj