title: Angular Observable: modify data before resolve
body: <p>I tried to transform data before resolve by such way, but subscriber gets non-transformed data.</p>
  
  <pre><code>@Injectable()
  export class OrderService {
      getAll(): Observable&lt; Array&lt;Order&gt; &gt; {
          let url = 'http://fakeapi.com';
          return this.http.get( url )
            .pipe(
              tap( (data: any) =&gt; {
                  /*
                  * MAKE DATA TRANSFORMATIONS HERE
                  */
              }),
              catchError( (err: any, caught: Observable&lt;{}&gt;) =&gt; {
                console.log('error while GET : ' + url);
                console.warn(err);
                return caught;
              })
            );
      }
  }
  </code></pre>
  
  <p>here is a subscriber:</p>
  
  <pre><code>this._orderService.getAll().subscribe( data =&gt; {
    this.orders = data;
    console.log('\nplanning-overview-page : _orderService.getAll : data ', data);
  });
  </code></pre>