How to dynamically create component instance with input/output from a service and inject it to DOM separately?

Question

In creating dynamic components in Angular 2, I found out that this process requires ViewContainerRef in order to add newly created component to DOM.

And in passing @Input and @Outputto those dynamically created components, I found the answer in the second link above and here.

However, if I were to create a service named shape.service that contains functions returning different shape components with some @Input like bgColor, I don't know how this service will create a component without specifying DOM location, and how the container-component receives this returned component (probably its type will be ComponentRef) from the service and injects it to the DOM container-component specifies.

For example, a service contains a method:

getCircle(bgColor:string): ComponentRef<Circle> {
    let circleFactory = componentFactoryResolver.resolveComponentFactory(CircleComponent);
    let circleCompRef = this.viewContainerRef.createComponent(circleFactory);
    circleCompRef.instance.bgColor = bgColor;

    return circleCompRef;
}

First question rises here, how do I make this.viewContainerRef point to no where for the meantime? The reason why I'm importing ViewContainerRef is to create component dynamically.

Second question is after container-component receives input-specificcomponentRef from the service, how will it inject to its DOM?

UPDATE: I think my question above wasn't specific enough. I'm in a situation where:

1. A parent component calls the service and gets the componentRef/s,
2. Creates an object including componentRef/s together with some other data and stores those created object/s into array
3. Passes it to its children as @Input,
4. And let each child inject componentRef to its DOM and use rest of the data in the object in other way.

That means the service calling component has no idea where those componentRef will get injected. In short, I need independent component objects that can be injected to anywhere, anytime I want.

I'm reading the rumTimeCompiler solution several times already but I don't really get how that really works. It seems like there's too much work compared to component creation using viewContainerRef. I'll dig into that more if I find no other solution...

Answer 1

Maybe this plunker will help you: https://plnkr.co/edit/iTG7Ysjuv7oiDozuXwj6?p=preview

As far as i know, you will need the ViewContainerRef inside of your service. But the component calling your service can add it as an parameter, like this:

(just a the service.. see plunker for full working example)

import { Injectable, ViewContainerRef, ReflectiveInjector, ComponentFactoryResolver, ComponentRef } from '@angular/core';

import { HelloComponent, HelloModel } from './hello.component';

@Injectable()
export class DynamicCompService {

  constructor (private componentFactoryResolver: ComponentFactoryResolver) { }

  public createHelloComp (vCref: ViewContainerRef, modelInput: HelloModel): ComponentRef {

    let factory = this.componentFactoryResolver.resolveComponentFactory(HelloComponent);

    // vCref is needed cause of that injector..
    let injector = ReflectiveInjector.fromResolvedProviders([], vCref.parentInjector);

    // create component without adding it directly to the DOM
    let comp = factory.create(injector);

    // add inputs first !! otherwise component/template crashes ..
    comp.instance.model = modelInput;

    // all inputs set? add it to the DOM ..
    vCref.insert(comp.hostView);

    return comp;
  }
}