title: Return when subscribing. ... Type 'Subscription' is missing the following properties
body: <p>I am subscribing a response from an Angular service:</p>
  
  <pre><code>  books: BookModel[] = [];
  
    constructor(private bookService: BookService) { }
  
    ngOnInit() {
  
      this.books = this.getBooks();
  
    }
  
    getBooks(): BookModel[] {
  
      return this.bookService.getByCategoryId(1).subscribe((payload: Payload&lt;GetBooksResponse&gt;) =&gt; {
  
        return payload.result.map((response: GetBooksResponse) =&gt; { 
  
          return {
            id: response.id, 
            title: response.title
          };
  
        });
  
      });
  
    }
  </code></pre>
  
  <p>When I add <code>return</code> to <code>this.bookService</code>, e.g., <code>return this.bookService</code> I get the error:</p>
  
  <pre><code>Type 'Subscription' is missing the following properties from type 'BookModel[]': length, pop, push, concat, and 26 more.
  </code></pre>
  
  <p>How can I use return to make this work?</p>
  
  <p><strong>Update: BookModel:</strong></p>
  
  <pre><code>export interface BookModel {
    id: number;
    title: string;
  }
  </code></pre>