Where is the best place to create class instances in Angular?

Question

Angular

I have an array of objects of type Layer:

let layers = [new ALayers(), new BLayers()];

I get them from a service groupLayersServicein a component:

@Component({
  selector: "layer-group",
});

class LayerGroup {
    constructor(private groupLayersService: GroupLayersService) {}
}

Next, in the component, I loop through the template and send a specific layer instance to the child component:

<div *ngFor="let layer in groupLayersService.getLayers()">
   <app-block-layer [layer]="layer"></app-block-layer>
</div>

Everything seems to be good. Further, in each component app-block-layerthere is a component app-treethat renders a tree based on the service that receives the layer layer.

The th component app-treeinjects a ready-made tree instance Treebased on subtypes: The

[new ALayers(), new BLayers()]

question is where to create tree instances, apparently in the component app-block-layer- it is in it that I specifically know what type new ALayers(), new BLayers()I am working with. So I can know what type of tree to create new ALayersTree(), new BLayersTree()so that the component app-treeinjects a ready instance. Moreover, the component does not know exactly - this new ALayersTree(), new BLayersTree()- but it knows that this is the type Treefrom which the new ALayersTree(), new BLayersTree().