message: Add call to photos variable from photoService
  There is no any variable `photos` in relevant component. So it must be referred from `photoService`.
diff: @@ -117,7 +117,7 @@ Next, move over to `tab2.page.html` so we can display the image on the screen. A
  <ion-grid>
  <ion-row>
  <ion-col size="6"
  - *ngFor="let photo of photos; index as position">
  + *ngFor="let photo of photoService.photos; index as position">
  <ion-img [src]="photo.webviewPath"></ion-img>
  </ion-col>
  </ion-row>
  