refactor(core): better service handling

Author: williamjuan027

core-demo/app/details/details-view-model.ts

@@ -1,12 +1,18 @@
 import { Observable } from "@nativescript/core";
+import { FlickService } from "../services";
 import { FlickModel } from "../models";
 
 export class DetailsViewModel extends Observable {
-  constructor(private _context: { flick: FlickModel }) {
+  private _flick: FlickModel;
+  constructor(private _context: { flickId: number }) {
     super();
+
+    this._flick = FlickService.getInstance().getFlickById(
+      this._context.flickId
+    );
   }
 
   get flick(): FlickModel {
-    return this._context.flick;
+    return this._flick;
   }
 }

core-demo/app/home/home-view-model.ts

@@ -20,14 +20,13 @@ export class HomeViewModel extends Observable {
   }
 
   populateFlicks(): void {
-    const flickService = new FlickService();
-    this._flicks = flickService.getFlicks();
+    this._flicks = FlickService.getInstance().getFlicks();
   }
 
   onFlickTap(args: ItemEventData): void {
     Frame.topmost().navigate({
       moduleName: "details/details-page",
-      context: { flick: this._flicks[args.index] },
+      context: { flickId: this._flicks[args.index].id },
     });
   }
 }

core-demo/app/services/flick.service.ts

@@ -90,6 +90,12 @@ export class FlickService {
     },
   ];
 
+  static getInstance(): FlickService {
+    return FlickService._instance;
+  }
+
+  private static _instance: FlickService = new FlickService();
+
   getFlicks(): FlickModel[] {
     return this.flicks;
   }