示例“ https://angular.io/tutorial/toh-pt6”的catchError无法正常工作

Question

如果您复制Angular的文档页面上公开的hero.service.ts类，则在调用catchError(this.handleError<any>('updateHero'))时会发现问题。

错误是：

遵循完整的打字稿类：

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

import { Observable, of } from 'rxjs';
import { catchError, map, tap } from 'rxjs/operators';

import { Hero } from './hero';
import { MessageService } from './message.service';

const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json' })
};

@Injectable({ providedIn: 'root' })
export class HeroService {

  private heroesUrl = 'api/heroes';  // URL to web api

  constructor(
    private http: HttpClient,
    private messageService: MessageService) { }

    /** PUT: update the hero on the server */
      updateHero (hero: Hero): Observable<any> {
        return this.http.put(this.heroesUrl, hero, httpOptions).pipe(
          tap(_ => this.log(`updated hero id=${hero.id}`)),
          catchError(this.handleError<any>('updateHero'))
        );
      }
    /**
       * Handle Http operation that failed.
       * Let the app continue.
       * @param operation - name of the operation that failed
       * @param result - optional value to return as the observable result
       */
      private handleError<T> (operation = 'operation', result?: T) {
        return (error: any): Observable<T> => {

          // TODO: send the error to remote logging infrastructure
          console.error(error); // log to console instead

          // TODO: better job of transforming error for user consumption
          this.log(`${operation} failed: ${error.message}`);

          // Let the app keep running by returning an empty result.
          return of(result as T);
        };
      }

      /** Log a HeroService message with the MessageService */
      private log(message: string) {
        this.messageService.add(`HeroService: ${message}`);
      }
    }

遵循错误：

Argument type (error:any)=>Observable<Cart> is not assignable to parameter type (err:any, caught:Observable<T>)=> never

Answer 1

我在这里找到了，我真的不明白为什么您也看不到错误。但这是在这里发生。

我更改了handleError的声明，参数的声明，并返回了Never类型。另外，我必须在记录期间更改错误对象的访问字段。

遵循最终代码：

/** POST: add a new hero to the server */
  save(): Observable<Hero> {

    var o : Observable<Hero>=this.http.post<Hero>(
        "http://localhost/FoodMail/master/src/webservice.php?q=SalEBrasa", c, httpOptions)
        .pipe(
            tap((hero: Hero) => {this.log(`added hero w/ id=${hero.id}`)}),
            catchError<Hero>(this.handleError2.bind(this))
        );
    o.subscribe();
    return o;
  }
  private  handleError2<T>(error: any, caught: Observable<T>) : never{


    // TODO: send the error to remote logging infrastructure
    console.error(error.message); // log to console instead

    // TODO: better job of transforming error for user consumption
    this.log(`${error.statusText} failed: ${error.message}`);

    // Let the app keep running by returning an empty result.
    //return of(err as T);
    throw  error;

  }