Learn TypeScript 3 by Building Web Applications

Implementing the bookCollection methods

The first method that we can add from the previous version of MediaManControllerImpl is reloadBookCollections(): void.

Here's the code that you can add for it:

reloadBookCollections(): void { 
    this.getMediaCollectionIdentifiersList().then(keys => { 
      this._bookCollections.clear(); // clear the current state 
      keys.forEach(key => { 
        this.loadMediaCollection(key).then(collection => { 
          this._bookCollections.set(key, collection); 
        }); 
      }); 
    }); 
} 

Notice that now we are extending from MediaService, we have removed the this._bookService. prefix and replaced it with this. in order to call the method from the parent MediaService class.

Also, since we manage the view with an Angular template, we don't need to call any ...