订阅可观察的Angular HTTP拦截器，然后返回next.handle，但抛出TypeError:您提供了'undefined' [英] Angular HTTP Interceptor subscribing to observable and then returning next.handle but throwing TypeError: You provided 'undefined'

问题描述

我有一个HTTP拦截器，在每个请求之前，我都要检查访问令牌是否过期，如果是，我从服务中订阅一个http.post调用，然后订阅它，当我得到一个新的访问令牌时，像这样调用next.handle(request):

I have a HTTP interceptor and before every request I check if the access token is expired, if it is, I subscribe to a http.post call from my service and then subscribe to it and when I get a new access token I call next.handle(request) like this:

        this.auth.refreshAccessToken().subscribe((token: string) => {
          this.auth.newAccessToken = token;
          request = request.clone({
            setHeaders: {
              Authorization: `Bearer ${token}`
            }
          });
          return next.handle(request);
        });

问题在于它抛出TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

这让我觉得我在那儿使http.post调用错误.

Which makes me think I'm making that http.post call wrong right there.

我还没有机会进行彻底的测试，但到目前为止看来一切正常.在返回整个地图之前，我有一个console.log，但是它没有触发，但是，其他所有方法都起作用，并且每当我获得新的访问令牌并且DID发生时，我都会在各处/权限更新currentUser，因此出于所有意图和目的似乎有效，这是更新的代码:

EDIT 1: I haven't had the chance to test this thoroughly but so far it seems that everything works. I had a console.log before returning the whole map but it didn't fire, however, everything else worked and I update the currentUser everywhere/permissions everytime I get a new access token and that DID happen, so for all intents and purposes it seems to work, here's the updated code:

          mergeMap(token => {
            this.auth.newAccessToken = token;
            request = request.clone({
              setHeaders: {
                Authorization: `Bearer ${token}`
              }
            });
            return next.handle(request);
          })

推荐答案

您不会在拦截器内subscribe()，而是将返回Observable<HttpEvent<any>>.这可以通过使用RxJS可管道运算符('rxjs/operators')来完成，例如点击 (针对设置newAccessToken等副作用)和 switchMap 或 mergeMap 与pipe()结合使用，返回类型为Observable<HttpEvent<any>>的可观察值来满足 HttpInterceptor 接口:

You would not subscribe() inside the interceptor, instead you would return an Observable<HttpEvent<any>>. This can be done by utilizing RxJS pipeable operators ('rxjs/operators') such as tap (for side effects like setting newAccessToken) and switchMap or mergeMap in combination with pipe(), returning an observable of type Observable<HttpEvent<any>> to satisfy the HttpInterceptor interface:

import { Injectable } from '@angular/core';
import {
  HttpEvent, HttpInterceptor, HttpHandler, HttpRequest
} from '@angular/common/http';
import { Observable } from 'rxjs';
import { switchMap, tap } from 'rxjs/operators';
import { AuthService } from './auth.service';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor(private auth: AuthService) { }

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return this.auth.refreshAccessToken().pipe(
      tap(token => this.auth.newAccessToken = token), // side effect to set token property on auth service
      switchMap(token => { // use transformation operator that maps to an Observable<T>
        const newRequest = request.clone({
          setHeaders: {
            Authorization: `Bearer ${token}`
          }
        });

        return next.handle(newRequest);
      })
    );
  }
}

这是一个示例.请检查日志以查看正在注销的关键信息.

Here is an example in action. Please check out the logs to see key information being logged out.

希望有帮助！

这篇关于订阅可观察的Angular HTTP拦截器，然后返回next.handle，但抛出TypeError:您提供了'undefined'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！