fix(data): correct AppEntityServices example in ngrx data doc page (#…

…2413)

closes #2280

projects/ngrx.io/content/guide/data/entity-services.md

@@ -135,43 +135,38 @@ The following `AppEntityServices` demonstrates.
 
 <code-example header="app-entity-services.ts">
 import { Injectable } from '@angular/core';
-import { Store } from '@ngrx/store';
-import {
- EntityCache,
- EntityCollectionServiceFactory,
- EntityServicesBase
-} from '@ngrx/data';
+import { EntityServicesBase, EntityServicesElements } from '@ngrx/data';
 
 import { SideKick } from '../../model';
 import { HeroService, VillainService } from '../../services';
 
 @Injectable()
 export class AppEntityServices extends EntityServicesBase {
  constructor(
- public readonly store: Store&lt;EntityCache&gt;,
- public readonly entityCollectionServiceFactory: EntityCollectionServiceFactory,
+ elements: EntityServicesElements,
 
  // Inject custom services, register them with the EntityServices, and expose in API.
- public readonly heroesService: HeroesService,
- public readonly villainsService: VillainsService
+ readonly heroesService: HeroesService,
+ readonly villainsService: VillainsService
  ) {
- super(store, entityCollectionServiceFactory);
+ super(elements);
  this.registerEntityCollectionServices([heroesService, villainsService]);
  }
 
- // ... Additional convenience members
-
  /** get the (default) SideKicks service */
  get sideKicksService() {
  return this.getEntityCollectionService&lt;SideKick&gt;('SideKick');
  }
 }
 </code-example>
 
-`AppEntityServices` injects the two custom collection services, `HeroesService` and `VillainsService`,
-which it also exposes directly as convenience properties.
+`AppEntityService` first injects the `EntityServicesElements` helper which it passes straight through to the base class constructor. 
+The "elements" enclose the ingredients that the base class needs to make and manage the entities you described in metadata.
+
+Then it injects your two custom collection services, `HeroesService` and `VillainsService`,
+and exposes them directly to consumers as convenience properties for accessing those services.
 
-There is no custom collections service for the `SideKick`.
+In this example, we don't need a custom collection service for the `SideKick` entity.
 The default service will do.
 
 Nonetheless, we add a `sideKicksService` property that gets or creates a default service for `SideKick`.