ngOnInit()被调用两次

我想通过 Angular 6 首先从webservice加载数据并在html中建立它 form . 我创造了一个 resovler 为了处理异步数据加载,但是组件中的观察者总是返回null,即使我可以看到web服务返回200并从浏览器中以正确的格式提供所有数据,下面是代码片段

更新

ngOnInit() 两次被叫来但是 resolver 只打过一次电话。

恩戈尼特() 提供cart对象,但下次cart对象为空。

我看不到任何来自角度控制台的错误,也看不到FireFox控制台的错误

@Injectable({
  providedIn: 'root'
})
export class CartResolver implements Resolve<ServiceCart> {
  constructor(private service: CartService) {}

  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
    const id = route.params['id'] ? route.params['id'] : null;
    if (id) {
      const existingCart = this.service.find(id).pipe(map((cart: HttpResponse<ServiceCart>) => cart.body));
      return existingCart;
    }

    return of(new ServiceCart());
  }
}

路由器

const routes: Routes = [
  {
    path: '', component: CartComponent,
    children: [
      {path: '', redirectTo: 'list', pathMatch: 'full'},
      {path: 'list', component: CartListComponent},
      {path: 'create', component: CartEditComponent, resolve: {cart: CartResolver}},
      {path: 'update/:id', component: CartEditComponent, resolve: {cart: CartResolver}}
    ]
  }];


@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})
export class CartRoutingModule {}

@Component({
  selector: 'app-cart-edit',
  templateUrl: './cart-edit.component.html',
  styleUrls: ['./cart-edit.component.css']
})
export class CartEditComponent  implements OnInit {
    cart: ServiceCart;
    .....
    ngOnInit() {
      this.isSaving = false;
      this.activatedRoute.data.subscribe(({ cart }) => {
        this.cart = cart;          // <--- always null
      });
    }

CartService(处理RESTful服务)

@Injectable({
  providedIn: 'root'
})
export class CartService {
    find(id: number): Observable<EntityResponseType> {
    return this.http.get<ServiceCart>(`${this.environment.config.servicesBaseUrl + '/api/carts'}/${id}`,
      { observe: 'response' });
    }
}

怎么了?