toast.service_v2.ts

import { Injectable, Injector } from '@angular/core';
import { Overlay } from '@angular/cdk/overlay';
import { ComponentPortal, PortalInjector } from '@angular/cdk/portal';

import { ToastComponent } from './toast.component';
import { ToastData } from './toast-config';
import { ToastRef } from './toast-ref';

@Injectable({
  providedIn: 'root'
})
export class ToastService {
  constructor(private overlay: Overlay, private parentInjector: Injector) { }

  showToast(data: ToastData) {
    const overlayRef = this.overlay.create();
    
    const toastRef = new ToastRef(overlayRef);
    const injector = this.getInjector(data, toastRef, this.parentInjector);
    const toastPortal = new ComponentPortal(ToastComponent, null, injector);

    overlayRef.attach(toastPortal);

    return toastRef;
   }

   getInjector(data: ToastData, toastRef: ToastRef, parentInjector: Injector) {
    const tokens = new WeakMap();

    tokens.set(ToastData, data);
    tokens.set(ToastRef, toastRef);
    
    return new PortalInjector(parentInjector, tokens);
   }
}