v0.17.0: Tratamento de erro

src/app/hero.service.ts

@@ -1,6 +1,7 @@
 import { HttpClient } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { Observable } from 'rxjs';
+import { Observable, of } from 'rxjs';
+import { catchError, tap } from 'rxjs/operators';
 import { environment } from '../environments/environment';
 import { Hero } from './hero.model';
 import { MessageService } from './message.service';
@@ -17,15 +18,29 @@ export class HeroService {
   ) {}
 
   getHeroes(): Observable<Hero[]> {
-    this.log('fetched heroes');
-    return this.http.get<Hero[]>(this.heroesUrl);
+    return this.http.get<Hero[]>(this.heroesUrl).pipe(
+      tap(() => this.log('fetched heroes')),
+      catchError(this.handleError<Hero[]>('getHeroes', []))
+    );
   }
 
   getHero(id: number): Observable<Hero> {
     const url = `${this.heroesUrl}/${id}`;
 
-    this.log(`fetched hero id=${id}`);
-    return this.http.get<Hero>(url);
+    return this.http.get<Hero>(url).pipe(
+      tap(() => this.log(`fetched hero id=${id}`)),
+      catchError(this.handleError<Hero>('getHeroes'))
+    );
+  }
+
+  private handleError<T>(operation = 'operation', result?: T) {
+    return (error: any): Observable<T> => {
+      console.log(error);
+
+      this.log(`${operation} failed: ${error.message}`);
+
+      return of(result as T);
+    };
   }
 
   private log(message: string) {